Towel travails (AirBnB)

I really don't understand how complicated it can be to hang a wet towel on the towel bar in the bathroom, as requested. Repeatedly, guests hang the towel on the wooden furniture or even leave it on the bed in the bedroom. 

Now, two guests in a row have hung the towel over the bathroom door. WTAF? The door already sticks - does it not seem problematic to leave a moisture-filled towel on a wooden door, where it will only make the door sticking problem worse? 

I tried putting the towel information more prominently, and repeatedly, in the AirBnB information, and, finally, I put a note in the bedroom. Still, the towel is often not on the towel bar.

Why is this an issue? The most recent guest continued to hang the towel on the door, even after I moved the towel to the towel bar on the first day. Why can't people follow this simple and clearly stated instruction? 

Why do I even have to ask - why don't people use the metal towel bar in the bathroom, the obvious place? How I can effectively communicate what seems to me to be an incredibly simple task? Why can't them seem to do this? Seems easy, both because I asked them to, but, also, out of common courtesy. I'm just flummoxed by this. 

ADDENDUM

I finally put a note on the shower door and the few guests since have managed to hang the towel there.