Why? Simple market dynamics. After 5000 years, the economics of running a traditional restaurant are essentially identical. That's because the lion's share of the value of a restaurant is the repeat and referral business, NOT in discoverability. That's why a fancy restro-bar on Glitzy Avenue shuts down after 3 months. For a good restaurant, the CAC should go to zero over time. The food should sell itself. By adding artificial market dynamics to this equation (mandatory advertising, artificially low unit costs, artificial discovery), you are removing that crucial, critical element, and the food will inevitably suffer. Burgers-R-Us can pay $1 per customer to appear at the top of your feed, serve you a shitty hamburger, then rename to Best Burger, and rinse and repeat.
Eventually consumers will wake up (many already have), and the traditional restaurants will escape with meaningful margins. Of course only a tiny fraction of restaurants that are started turn into surviving businesses, as has been the case since time immemorial.