Because C is not open source, Perl is. (Yes, there are open source C compilers, but which really has the largest sell-thru?) Show me the C equivelant of CPI.pm and DBI and I'll consider the language, provided you can also point me to something that teaches me how to think in pointers.
Perl is for the average person, for the individual who just wants to get something done without having to relean every fscking wheel that everyone else has had to learn.
That said, Perl is not the only solution and only a fool would think that it can do everything. Use the best tool for the job.