[Fedora-packaging] Why don't we write in guidelines that BR: perl is mandatory for perl packages?

[Parag Nemade]

Hi,
    I have a discussion going on
https://bugzilla.redhat.com/show_bug.cgi?id=979677 where my basis of
discussion is that "BR: perl is mandatory" is not written in any
guidelines. Technically, I can understand what perl people there are trying
to tell me.
    So, question is why is it so hard to write in perl guidelines that perl
packages should BR: perl?

Regards,
Parag.