I agree with Benjamin, that it is not a requirment to have a "fursona". Though I don't consider myself a fur as such, I feel I do have a broad understanding of the various aspects within the fandom. Regarding your issue, one thing I have found with many furs, that many are simply animal fans. Nothing wrong with that at all, but that is what they are. Though, they do often have a good understanding of animals, inparticular their favourite one(s), obviously. So those people would create a fursona based on their favourite animal, or animals. These furs are the sort that do tend to change their fursona quite a bit. The other type of furs are animal spirits. These furs have, or strongly believe themselves to have the spirit of a particular animal. Whereas the other furs choose their favourite animals, these sort of furs almost have the animal chosen for them. What is interesting is that both groups of furs have those that do have fursonas, and those that don't. One view I have is that because a lot of furs are artists, and/or art fans, they create fursonas for themselves to draw, and for others to draw. Maybe they do it because they like art, maybe they do it because they're vain, I don't know. One thing to remember is that the furry community is too broad a thing to generalise. There are all sorts of people, from all walks of life in the fandom, and so to generalise is difficult, and often inaccurate. Anyway, I'm rambling. These are my thoughts, and I hope my words have been of some help to you.