Because the actual cost to AWS for a customer accidentally racking up an expensive bill is minuscule compared to the cost of that bottle of wine to the restaurant.

Amazon also has an interest in keeping their customers happy, and keeping usage growing. A customer who gets a refund for accidental or fraudulent usage is much more likely to remain a loyal customer, and hopefully spend more on the platform in the future. A restaurant, while in the hospitality industry, is likely more concerned with their razor-thin margins.

Also I would expect the true motive in your example is that the restaurant-goer is trying to scam the restaurant out of an expensive bottle of wine, and I'm sure most restaurant managers would agree with me. The AWS customer is not only more likely to have made an honest mistake, but AWS support has tools available to look at the usage and make a more nuanced decision as to whether or not the customer is telling the truth.

(And I have witnessed quite a few situations where Amazon has written off usage bills in cases like this. So clearly they agree with me on this, at least some of the time. Not all of the time, of course, as the grandparent poster can attest to.)