By design or default, many vets permit the pet food industry to act as their proxy when it comes to nutritional decision-making for their clients. Since diet is a VERY big thing to get wrong, this can have a serious, negative impact on the health and well being of your cat - and downstream consequences for your peace of mind and your pocketbook.
Many of us are wired to accept with (blind) faith the advice of vets, since they are the trained professionals who spent years in school learning how to save animal lives and have so much more accumulated knowledge than us "lay folk."
Add to this the fact that in many or most vet clinics, foods with "prescription" labels line the shelves and walls, creating the impression that these diets are closely scrutinized and tested the way human prescription medications are. Unfortunately, however, this is simply not true. While Hill's obtained trademark status for the phrase "prescription diet" over 20 years ago, in the words of an FDA official, " ' Prescription diet’ is an industry-coined term and holds no legal meaning.” Yes - Prescription Diet® is a registered trademark of Hills® Pet Nutrition, Inc.®.
This shifts responsibility to all of us cat caregivers to screw up our courage - and roll up our sleeves at least a little - to become as educated and informed as we can about what's truly healthy for our carnivore friends, especially (but not only) when they're facing a health challenge or crisis for which a vet is recommending a "prescription" diet.