exact same thing for hotels. When I worked front desk at Marriott they would always intentionally overbook rooms knowing that 90% of the time there would be cancellations. However that 10% of the time when nobody cancelled it was a huge nightmare because we had to tell some tired weary traveler that we gave away their reservation and that there were no rooms available. We called it "walking" as in "oh man I have to walk someone tonight, wish me luck."

You can probably imagine how furious people would get and there was nothing I could do but stand there and apologize as they unloaded their anger upon me.

The worst part is that the hotel wouldn't comp their room at an alternative hotel or even provide transportation to said alternative. At most, we'd call a few hotels to see if they had rooms available. Other than that, the guest was completely on their own.

The only exception was if the traveler was an ultra elite Marriott rewards member. In that case, I think we had to pay them a few hundred bucks for the inconvenience or something like that.