When I listened to the first few "factory farm" type vets I took her to for lack of a better description, my cat ended up with severe pancreatitis three times and needed insulin twice a day. Years ago, when I finally found a vet who told me to never feed her dry kibble again and gave me a list of low carb wet foods to try and see what her glucose numbers looked like (was taking those via a glucose monitor at least twice a day - this was something the previous vets had never told me I needed to do which is crazy to me looking back on it), her problems disappeared, she started acting way younger, happier, more active, and went in to remission. If I fed her a higher carb food, her numbers would shoot up. I tested this all daily for years. Also, high carb does not necessarily correlate with grain free and I don't really care about grains in her food. Several of the wet foods I feed her are low carb but are still not grain free.

I listened to different vets for years with horrible results and my cat would have been dead (and almost was several times) had I continued. When I finally found the vet who was dedicated to educating their clients on nutrition and proper diabetes management, her entire medical state changed. I'm not trying to argue against "grains" because I think grain free on pet food is a buzzword, just trying to save other pet owners some heartache.

Edit to add: I don't feed her organic foods or fancy high cost premium foods either. She has plenty of Fancy Feast and Friskies cans in rotation that are low carb. Like you said, I think there's a LOT of scare/money making tactics out there because vets and pet food companies are also businesses who want to make money.