But you've strawmanned this. Do you go to the gym, put your towel down on the leg press machine, and then go to the juice bar for a drink? Because that's what we're discussing here: taking away a finite resource so that others can't use it.

People with unused gym memberships who don't show up haven't promised anything. They didn't make an appointment with a personal trainer, they don't have machines reserved, there's no implicit contract to exchange limited resources for a membership fee. Your membership fee gives you access to these resources, not a guarantee of their usage. If you go to the gym and every treadmill is in use, then you don't get a treadmill for now. You just wait for a treadmill.