So what happens in the hypothetical that the food sucks and the bill for $300 comes to you. Do you just not pay?

You are implicitly believing in their reputation by selecting the fine dining establishment. I don't really do fine dining so excuse me if this is ignorant, but it seems to me you don't really have recourse after the fact.

Problem is that there are millions of potential customers all who may or may not be flakes. When business could be make or break by one reservation backing out, they have much more to lose way more often than you having an awful experience at a reputable establishment. Tock makes sense in this scenario but you seem like you're being completely unempathetic to the economics of the situation.