Because I love Ruby. I think it is a brilliant language. It is the first language that I have come across where the creator has really thought about what he is doing, and made a well thought-out and well designed language. It is fully object-oriented (unlike C++ and Java), and always has been (unlike Python) which gives a lot of functionality in a sensible and consistent manner - its object orientation is not a horrible, horrible kludge (like Perl's is). It has some really nice features, such as run-time (re)definition of methods on objects and classes. Don't be off-put by having to get yet another language, it is really tiny (less than a megabyte), and has no dependencies that shouldn't be met by any relatively modern Unix-type OS.
Enough chatter from me - go check it out, I'm sure you'll be impressed.