Bash scripting: When to use variable, when function?

basic, innocent question: In bash scripting, why ever using a function, if one can set a variable containing command substitution with the essence of the function - a certain command or set of commands, which is supposed to output a certain value? In other words: Does it matter, if one defines a variable, or a function for a certain, desired output? When and why to implement it as a variable? When and why it's better to implement it as a function? Example: Let's say, there is a directory on your system, which contains a lot of sub-directories in 1st level, and you want to find out with a bash script, what's the most recently modified. In a bash script, you can define a variable

for it, and print out its content on demand:

#!/bin/bash

#    latest-directory-displayer
#                                                                                                                                                                                                                    
#    Copyleft 🄯 2024
#                                                                                                                                                                                                                    
#    This program is free software: you can redistribute it and/or modify                                                                                                                                            
#    it under the terms of the GNU Affero General Public License as published by                                                                                                                                     
#    the Free Software Foundation, either version 3 of the License, or                                                                                                                                               
#    (at your option) any later version.                                                                                                                                                                             
#                                                                                                                                                                                                                    
#    This program is distributed in the hope that it will be useful,                                                                                                                                                 
#    but WITHOUT ANY WARRANTY; without even the implied warranty of                                                                                                                                                  
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                                                                                                                                                    
#    GNU Affero General Public License for more details.                                                                                                                                                             
#                                                                                                                                                                                                                    
#    You should have received a copy of the GNU Affero General Public License                                                                                                                                        
#    along with this program. If not, see .                                                                                                                                           

# Displays what's the most recently modified sub-directory within
# current directory.

# Tool variable set                                                                                                            
find="/usr/bin/find"
sort="/usr/bin/sort"
tail="/usr/bin/tail"
grep="/bin/grep"
sed="/bin/sed"

# Variable set                                                                                                                 
rece_dir="`"$find" . -maxdepth 1 -type d -printf '%T+ %p\n' | \
                   "$sort" | "$tail" -1 | "$grep" -o "/.*" | \
                   "$sed" 's/ /\\\&/g;s+$+/+'`"

# Function set                                                                                                                                                                                                     

################################## Main part ###################################                                                                                                                                     

printf "$rece_dir\n"
exit

Cute. But why not doing it like this?

#!/bin/bash

#    latest-directory-displayer
#                                                                                                                                                                                                                    
#    Copyleft 🄯 2024
#                                                                                                                                                                                                                    
#    This program is free software: you can redistribute it and/or modify                                                                                                                                            
#    it under the terms of the GNU Affero General Public License as published by                                                                                                                                     
#    the Free Software Foundation, either version 3 of the License, or                                                                                                                                               
#    (at your option) any later version.                                                                                                                                                                             
#                                                                                                                                                                                                                    
#    This program is distributed in the hope that it will be useful,                                                                                                                                                 
#    but WITHOUT ANY WARRANTY; without even the implied warranty of                                                                                                                                                  
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                                                                                                                                                    
#    GNU Affero General Public License for more details.                                                                                                                                                             
#                                                                                                                                                                                                                    
#    You should have received a copy of the GNU Affero General Public License                                                                                                                                        
#    along with this program. If not, see .                                                                                                                                           

# Displays what's the most recently modified sub-directory within
# current directory.

# Tool variable set                                                                                                            
find="/usr/bin/find"
sort="/usr/bin/sort"
tail="/usr/bin/tail"
grep="/bin/grep"
sed="/bin/sed"

# Variable set                                                                                                                 

# Function set                                                                                                                 
display_latest_dir() {
    "$find" ./ -maxdepth 1 -type d -printf '%T+ %p\n' |
    "$sort" |
    "$tail" -1 |
    "$grep" -o "/.*" |
    "$sed" 's/ /\\&/g;s+$+/+'
}

################################## Main part ###################################                                               

display_latest_dir
exit

Same output, same basic inner workings, but one over variable, while the other over function. A minor difference I've spotted was different escape requirements. As soon as you put your set of commands into a variable as command substitution, it probably needs 1x more

\

wherever you've escaped with a back slash. Why not always use variables, instead of functions? Why not always use functions, instead of variables?