1. Because the code is so old we don't want to have an intern figure out how to do it. (Adding a switch for a new PCRE, such as /P, is hard) Oh, and reading and understanding licenses is HARD?!?!? WTF?
2. It would break backwards-compatability if we did it. (Well, duh).
I understand now it may not be worth it (powershell/.net is the future or whatever), but really, at no time in the 90's and 00's did you think it may be worth some time?