Hmm,

Most of the responses here are sort of silly. The many wolf therians I know are nothing about what they may have read in the books, they just feel wolf.

And if you look at the community as being made of individual therians who may be of one theriotype or another and treat each of them with the same amount of respect as you do to yourself and your own therianthropy, you will notice that there is no particular reason.

And while the statistical playing with numbers may be very interesting, an appropriately scientific analisys of facts will give you the very clear answer: It may be a large variety of factors, but on the other paw, it's all really just a big coincidence.

It's the same as with asking why there is so much grass and leaves in the world and just as much a stupid question unless you're interested in very random details IMHO.