I believe there was a Planet Money (or similar) piece about this recently. There are already services to enable dynamic pricing for restaurants. E.g. on super bowl Sunday ordering wings will be more expensive. (They don't like the term "surge pricing" though:-)

However it can also go the other way and lower prices to incentivize demand during slow periods like middle afternoon.

Can't say I blame restaurants for this. As many other comments mention, it is all about having good UX