I get the feeling that even vets are stuck in their old ways, just like how people are after owning cats for so many years and caring for them one way, assuming it's okay because it's always worked out before. When we brought Mo into a new vet a few months ago, it was specific to a digestive issue so the vet had to ask what kind of food he was receiving. She's a young vet and had graduated pretty recently, so she flat out told me the more wet food, the better. I have yet to see a vet that tried to sell me food.
Perhaps they get used to dealing with older pet owners too, who may be especially stubborn and not want to have the added cost of feeding anything but the dry that's readily available to them, or the dry they find so convenient. The vets that do know better learn to tread lightly when suggesting changes, even if it means the animal would be better off, because it makes for unhappy owners who will sing the praises of their grocery store kibble and take their business elsewhere - potentially to a vet who will agree with the owner that yeah, kibble is just great. Just while I was in the waiting room at said vet's, three people walked in and grabbed huge bags of Royal Canin dry to buy.
Ideas about an appropriate diet for cats have been around forever, and kibble has been the convenient go-to for pets since something like the 1800s. That's a long time for something to be considered good for a pet, and especially because it comes as conveniently as it does and it's been marketed so strongly over the years, people assume it's still the standard. The pet food companies don't help by continuing to make kibble, especially the lower quality ones because it makes them a TON of money. We can't expect everyone to know, understand, and embrace and for crappy kibble to just disappear over the course of a couple decades now that better information is becoming widespread to the masses. A lot of these masses don't want to admit they've potentially been wrong their (or their cats') entire lives! Not to mention there's still a lot of conflicting information published and online that confuses even those with the best of intentions for their pets.
If you compare it to other pet industries that are younger, like exotic pets, vets will never push something that's already been proven to be bad. The first thing an exotic vet will ask you, regardless of why you're visiting is what you feed your pet. I think in this case, exotic specialists are still learning so much on the go that they didn't know about the animals they treat as recently as ten years ago, they can't afford to be stubborn about replacing and replenishing their knowledge as they go. If they miss one conference and misdiagnose one patient, it doesn't take long for that owner to Google their way to their own answer and place blame for the vet not knowing better when the information can be found by them right on the internet.
There seems to be more blissful ignorance and the willingness to stick to the "tried and true" familiarities.