I’ve been to some hotels where the pool attendants will periodically come round and any towels that have clearly been laid down to ‘reserve’ places get removed.
We’ve regularly seen people who have reserved prime spots with a load of parasols etc. come back in the late afternoon having not been there all day & then pick up their towels and wander off; obviously been out for the day, but reserving ‘their’ spot anyway.
I’d happily move towels that have been in the same spot with no occupancy for a couple of hours, but my Wife doesn’t want the potential aggro while on holiday so always tells me not to bother.