I think scam isn’t the right word. What I think you are implying is that they will push the script food on animals that don’t actually need it, which I have no doubt happens.

It’s not about the food it’s about the doctor you do or do not trust. Ask the doc about it, have them explain why it’s necessary, get a second opinion, etc. if they’re pushing unnecessary script food they probably do the same with other things.

You can protect yourself if you put in the effort.