Why verbal instructions don't scale
An instruction given once, in person, works until the person who heard it is unavailable. A written checklist works regardless of who's doing the turnover that day, and it's the only version that's checkable after the fact.
Clean and ready aren't the same thing
A cleaner can do an excellent job on cleanliness and still miss something a host would call ready: a low battery in a remote, a drained coffee supply, a lightbulb that's been out for two turns. A checklist catches the category of problem a cleaning pass doesn't.
Why this rarely gets written down
Most hosts know exactly what 'ready' looks like in their own head. Writing it down for someone else feels unnecessary right up until a different person is doing the turn, and by then it's a live problem, not a planning one.