Why Debian requires manual edit of /etc/apt/source.list to receive LTS updates?

Why in Debian, you must manually edit your /etc/apt/source.list in order to receive LTS updates as explained in the [official Debian LTS Wiki](https://wiki.debian.org/LTS/Using) ? Why it's not like Ubuntu where LTS updates arrive without the need of this manual change on /etc/apt/source.list? this is the an original /etc/apt/source.list after the install

deb http://deb.debian.org/debian  buster main
deb-src http://deb.debian.org/debian  buster main

deb http://deb.debian.org/debian-security  buster/updates main
deb-src http://deb.debian.org/debian-security  buster/updates main

# buster-updates, previously known as 'volatile'
deb http://deb.debian.org/debian  buster-updates main
deb-src http://deb.debian.org/debian  buster-updates main

and this is the one from [official Debian LTS Wiki](https://wiki.debian.org/LTS/Using)

deb http://deb.debian.org/debian/  buster main contrib non-free
deb-src http://deb.debian.org/debian/  buster main contrib non-free

deb http://security.debian.org/  buster/updates main contrib non-free
deb-src http://security.debian.org/  buster/updates main contrib non-free