Their original "point" was to sell tires, and then they became somewhat famous in their ratings. They also give out "keys" to motels, and one BnB near us (we've been given a tour, it is quite nice, a bit pricey). The claim to rate restaurants purely on food, not service or anything else, which I tend to doubt, but whatever.
It's somebody's opinion, maybe several opinions, but think of how many places they can't possibly rate. A city also has to pay them to come into town.
I'm not interested in paying nearly $400 per person for dinner, no matter how good. Part of dining out for us is simply having interesting food, and not cooking and cleaning etc. I've commented before about how I did not care at all for the 3 star place in Marseille to which I was basically forced to try. Maybe I had a bad attitude.
