It was hardly ever the same business making the image and the food.

I'll say that again - when a restaurant has pictures of food, those pictures are often from stock, not actual representative shots of the food the restaurant sells.

This especially applies to fast food and tourist eateries. (Upmarket restaurants don't usually have photos at all.)

Just Eat in the UK has a policy of requiring actual dish shots, but that's not the norm.

Hmm. This is not a common occurrence for me (in the US), has happened maybe once in my life that I can remember. I would have exactly the same issue with that, maybe worse since with AI slop I can at least tell before I've spent the money.