Not every restaurant of course, but there’s a reason that restaurants regularly fail, especially in cities, and I don’t think it’s because the owners are spending it all on yachts.
I think a lot of them are in debt up to their eyeballs and that’s why they fail. They also usually make up for the lower margins on food with better margins on drinks, but there’s a margin on every item regardless.
Rent is also a factor. Commercial real estate is not cheap.
And some just plain suck. The food sucks, the prices suck, the service sucks, or the location sucks.
There are myriad reasons why restaurants fail, and I doubt it’s all because of low margins.