A thorny subject. The CG wants to get best financial return. Some CGs also want to get best use out of the CG.
Yes it is nice to have sites paid for. Even better to have them paid for & being enjoyed. Hotels can be notified for a late arrival. The difference is you can't tell if a hotel room is occupied or not.
The policy of a site being held till the next day does not help the camper who is there looking for a site the day before. The weekend warrior cannot take a day off work to go put his camper in a site on Friday. He may also have kids activities on Friday or Saturday morning.
There is no easy way that is fair to all.