Uhm well a big reason is also I guess because perl usually is open-source so when a company develops software with a nice and new feature others will simply copy it etc etc...
But for really big applications tbh I would choose C++ and not perl for lots of reasons. Perl is great for small scripts, webpages and small apps but for really big stuff...hmm I guess C++ for example is just the better choice even if it would be possible with perl.
Wages is another topic, I think good perl-coders should be paid equal to Java/C-Coders, but most perl-coders aren't as skilled as C-people usually (That's my personal experience, may be wrong).