As far as Unicom etiquette and behavior go, this is certainly lower on the list than taking off against traffic or taxiing through others, etc, but it’s not an insignificant factor in preventing runway incursions on Unicom.
When you land and someone lines up behind you, very likely they are just waiting for you to announce when you are clear of the runway, rather than actually visually verifying that you are indeed clear.
While at MPTO within the last couple of hours, there was an extended period of time where it was Unicom. Surprisingly, everyone (well…almost) behaved rather admirably, with one exception:
Not a single pilot who announced clear of all runways actually was. Some were even still pretty much on the center line.
When someone is behind you awaiting this call out to takeoff, it’s important that you make it only when you are actually clear, so that they don’t end up starting their takeoff roll with you still smack in the middle of the runway.
And, again, clear does not mean “I’ve started to turn off” it means fully past the hold short line.
All of these pilots have already announced “clear of all runways.” None of them are: