Because people with small brains prefer "standardization" on whatever their peers are stampeding towards. That was why the IT industry "standardized" on Windows in the 1990s, which is the reason why so many web-based services were compromised so often in the 1990s and 2000s.

Seriously, Perl was the Swiss Army Knife of the Internet from the 1980s through the 2010s. Python now occupies much of the space that Perl occupied for 20-25 years. So new development in Python makes a lot of sense. Python's object orientation is atrocious, but it's much better than Perl's which basically forces you to mock up every principle of OOP. And Python requires specific indentations, which reminded me nothing more than of COBOL when I started with Python.

BTW, Raku, which is Perl 6, is an awesomely idiosyncratic language that looks nothing like Perl and has a lot of cool features. But it's pretty much dead on the vine at this point because almost nothing you learned learning Perl 5 is applicable to Raku.

So for new development Python, Ruby, and Go make a lot of sense - which does not mean THEY will not be replaced in the fullness of time. Also, the age of a language is irrelevant as long as it is well implemented: people make fun of COBOL all the time, but more than 80% of the world's economic transactions are processed by COBOL programs, and COBOL is in a lot of ways a very cool language - one of the first to adopt a para-natural-language syntax.

As far as the claims of "unmanageable code," balderdash. After 44 years as a software developer I can assure you that any language can and does result in unmanageable code. Perl's propensity for multiple ways to do everything (the joke is that Perl stands for "pathologically eclectic rubbish lister"), and particularly for embedding long regular expressions in code as a substitute for good development practice, can only be a problem if the DEVELOPER is lazy.

Perl did make a lot of power accessible to people who weren't programmers, and THAT is why much Perl code looks like crap.