And there is yet-another reason:   core software components of a particular distro, such as the package-manager itself, might be written in Perl.   Thus, even a “slight” change to the packaged Perl distribution might introduce “breaking changes” with many repercussions.   It should also be considered that, when any change is made to the language interpreter, most if not all packages for that interpreter might have to be updated and/or recompiled.   The “ripple effects” can be quite substantial.