There are sadly a lot of vets who are more interested in their profits than health - a dog on vet kibble is usually more likely to come back in over and over again, where a lot of raw dogs just don't get sick. Of course they're going to say raw is a bad thing!
Or they see dogs fed raw that are fed wrong and again assume it's the whole diet.
I had a lady complain up and down that her vet bills were insane - she's feeding the vet based kibbles and in constantly for ear issues with the dog. Yet won't try raw because the same vet said it was bad for her dog.... Told her it wouldn't be any worse to try raw for a while and it might just solve the problem, but of course the vet isn't going to make money on a healthy dog.....