A reservation is a contract...sort of. If you have high level status with a chain in premise you should be/are entitled to some form of compensation. But if not, there are no laws that I'm aware of that entitle you to anything. The whole idea of getting "walked" is more about tradition and PR so that you might come back in the future rather than an actual legal obligation.

Parts of the reservation process are all a big game. If you don't show up, the hotel will attempt to charge you...unless of course you're a frequent enough guest then we might look the other way and release the GNS and never bill it. Just like plenty of guests make reservations with "bogus" credit card numbers that they know will allow them to hold the reservation, but if they don't show up they can't be charged. Just like some properties try to get around that by pre-authorizing cards the day of or day before arrival and if you're card comes back declined, you'll get a phone call or email asking for a valid MOP by X time less you're reservation will get cancelled. Sure you could try and get a digital key early on the day of arrival to increase your chances of getting a room...unless the property does something greasy like keeps all or a certain percentage of their rooms vacant dirty or out of order which will be prevent digital key from being used on those rooms/room types. What should be black and white is actually very grey and situational more than an actual standard that applies to all reservations.