Why do the vet techs say they don't like Hill's - that is what the vet's push!?

I have always wondered why they "push" the Hill's Science Diet because I've read a lot on nutrition and their food does not seem to be very nutritional. Some vets (one I just left) think dogs and cats are omnivores and will eat anything and they will if we feed it to them. I found a wonderful Alternative Vet but she is 29 miles one way from my home and so doing the math that's 58 miles a trip and my dog get car sick so she gave him some herbs for that. Last trip we made it without vomiting - yeah. I love her but with 7 dogs cannot really afford to cook for 7. We just switched from Wellness to Merrick Granny's Pot Pie kibble. Hope it is okay for them. My other dog that got sick had high ph and a mysterious gastroenteritis which the vet (I just left) thought was pancreatitis. She kept talking down to me asking me questions like did they eat something they shouldn't have? I am a professional pet sitter and have 7 dogs and 6 cats and I certainly know what to look for. She's been to my house and knows my surroundings. They could not get into anything without me knowing. Idiopathic gastroenteritis??? Not sure how. Wellness chicken food has not looked right the last two bags and so I am switching. All my other dogs are okay. One I cook for and the other 6 all ate the Wellness food - w Paul Neuman canned - flax - fish oil - yogurt & MSM. Any comments back are appreciated.