Disclaimer: I don't see myself as sysadmin and do not claim to be the authority here.

It's just common sense: (and already said, but since you are addressing me...)

The system installation of Perl is part of OS critical processes and can be changed by OS updates.

OTOH applications like web-services have other requirements.

In a one-user box like my laptop w/o critical processes conflicts may be rare and easily resolved, but in large scale installations (multi-server, -user, -responsibilities) you want to keep full control.