SQL Server Installer appears to be resetting MSDB Recovery Mode to Simple

Everytime we upgrade a SQL Server installation (service pack or cumulative update), **msdb** is changed from FULL recovery mode to SIMPLE recovery mode. I understand that the **msdb** database doesn't change much and it is common to have it in SIMPLE, but I'm wondering why the installer is changing it. It is causing errors in my backup software. Here is an extract from the installation logs:

2020-02-15 03:06:38.25 spid8s      Starting execution of MSDB.SQL
2020-02-15 03:06:38.25 spid8s      ----------------------------------
2020-02-15 03:06:38.35 spid8s      Configuration option 'allow updates' changed from 0 to 1. Run the RECONFIGURE statement to install.
2020-02-15 03:06:38.35 spid8s      Configuration option 'allow updates' changed from 0 to 1. Run the RECONFIGURE statement to install.
2020-02-15 03:06:38.56 spid8s      Checking the size of MSDB...
2020-02-15 03:06:39.41 spid8s       
2020-02-15 03:06:39.41 spid8s      Setting database option TRUSTWORTHY to ON for database 'msdb'.
2020-02-15 03:06:39.41 spid8s      Setting database option RECOVERY to SIMPLE for database 'msdb'.
2020-02-15 03:06:39.46 spid8s      ----------------------------------
2020-02-15 03:06:39.46 spid8s      Finished execution of MSDB.SQL
2020-02-15 03:06:39.46 spid8s      ----------------------------------
2020-02-15 03:06:39.46 spid8s      -----------------------------------------
2020-02-15 03:06:39.46 spid8s      Starting execution of MSDB_VERSIONING.SQL
2020-02-15 03:06:39.46 spid8s      -----------------------------------------
2020-02-15 03:06:39.47 spid8s      -----------------------------------------
2020-02-15 03:06:39.47 spid8s      Finished execution of MSDB_VERSIONING.SQL
2020-02-15 03:06:39.47 spid8s      -----------------------------------------