Because when you always take advantage of all that flexibility, you end up with Perl.
Everyone was always so excited to show off their mastery of Perl and do fancy things that it was very hard to maintain, and Perl got a reputation as a "write-only"[1] language.
You should follow the principle of least-surprise, and follow the idioms of the language. It's great to have the flexibility when you absolutely need it, but that should be reserved for rare cases and be very well commented.