In recent years, I have not had any booking problems whatsoever. Only problem I had more than 10 years ago was about arriving very late and finding that my room reservation had been released and they were full. Luckily it was a big chain hotel which had another property nearby and was able to get me a room there for the night and then resume my original room for the rest of the week long stay. This was very busy conference week and all 3+ star hotels were full in the area.
In my experience (not very big hotel) - the emphasis was on full occupancy - rooms would only be held (with other guest with booking at the counter) in rare circumstances (eg we knew an incoming flight was delayed and we were certain the other guest would arrive. Even then we might bump the other guest if it meant we had more time to scramble to find an alternative room for the guest that hadn't shown up yet).