Lots of "sane" people would (at least for Perl 5). I know it's not "the new hotness", but Perl 5 is still an incredibly useful language that a lot of people know (present company included). There are extensive libraries available for doing a lot of things that need to be done in day-to-day business. There are plenty of perfectly legitimate places to use it in new development.
The Perl 5 porters development list has a decent amount of traffic ( http://www.nntp.perl.org/group/perl.perl5.porters/2017.html ). And Perl 5 still has a good number of active contributors ( https://www.openhub.net/p/perl/contributors ). Also, The CPAN has plenty of modules with daily activity ( http://search.cpan.org/recent ).
Even if you would not choose to do new development in Perl 5 (because of other language preferences, or whatever), that does not mean it is unreasonable (or "insane") for others to do so.
Whether Perl 6 will ever catch on, I don't know. The language has a lot of features that look interesting, and I think it could also be very useful. I personally have not had time to look at it much yet, but probably will when I don't have higher priority things in life preventing me from doing so.
