I think in a lot of respects, vets with their food recommendations are just like doctors with their drug recommendations. They get kickbacks. If they tell you they don't, but they have any types of ads in their office or suggest specific brands, etc. they are flat out lying to you.
The doctor I went to for years was one of the only docs around here who was unaffiliated with any big medical group like Bon Secours or Sentara. The reason he did that, is because he didn't want to be forced to push medicines on patients if he didn't think it was the best for the job. As a result, his office didn't have a single ad or product in the entire place with any pharmaceutical company or name of any drug on it, and he had no samples to give. To me, vets that are similar are the only ones you can truly trust. if they recommend something specifically by name, there's generally a reason for it. Especially if they insist on a particular brand, dead giveaway.
My first Border Collie ate Moist & Meaty for over a decade - at the recommendation of her vet. Without checking the ingredients, we took her word for it. After years of feeding it to her, her teeth rotted out even with regular cleanings, greenies, etc. Come to find out, Moist & Meaty is overloaded with sugar.
We switched vets, and the new vet instead of recommending things by name, instead pointed us in the direction of the type of food to look for, and the ingredients to avoid. That's why we settled on Petfresh. And this vet even told us never to let a vet tell you by name what to buy, because they have their motives.