A lot depends on the property. If a base-level chain hotel, if it is handled at all, it is largely handled by software which can then be manipulated by a room assigner (depending on property size) who might be the FD clerk the night before. If you are looking at a real luxury (because it is, not just because a chain uses some fake "*" rating), there is a great deal of effort put into the process and it includes knowing what a guest's minute preferences are. If you asked for an extra pillow last time, there will be an extra pillow already in the room and so on.

Leaving rooms empty make no economic sense whatsoever, unless you want to book the extra rooms to keep them empty. If you are staying at a property where you can hear snoring though the walls, you should consider staying at one with real walls !