Reason for self building packages?

[AdamCoulterOz]

I currently use this project extensively to install php extensions paired with the docker images from docker hub repo library/php. Can I ask why this is the recommended approach instead of using apt packages which are precompiled for a given linux distro? For example nearly all php modules, for nearly all php versions, built for nearly all recent versions of Debian and Ubuntu here: https://deb.sury.org ?