Well, I can't speak for anyone else, but I don't intend to use any characters other than the dinosaurs. When I first saw SC I noticed that not too many people were using them and that they were full of potential. Also, I think most of the creators here tend to stick to a stable of five characters or so, sort of like how Bill Watterson made it a rule not to introduce new characters into Calvin and Hobbes after the first year or so (and the one time he did introduce a new character he soon regretted it). In comics this is usually a good idea. It's like a painter or a designer using a limited pallette to create a more unified work of art.
Jesus Christ, do I sound pretentious. I think about comics way too fucking much.