There's arguments to be made for sorting different ways. Sorting by hits favors multi-chapter works over single-chapter works, certainly; but it also favors old favorites that people re-read often. Because you can only kudo once per fic, but a favorite fic you might read many times. In which case, hit count is a more accurate reading of how much you enjoy a fic than a kudo. (And, in any case, I tend to prefer longer stories, so the fact that it favors long stories isn't exactly a downside ;) )