I leave one bath towel and one face clotch per guest. For stays for four or more nights I leave two towels. The bathroom is shared and I change the hand towel once a day when having guests. More often if needed/many guests.
Laundry is extremely resource demanding and I don't want to contribute to excessive usage of water and energy. Washing linen that has been slept in for one night is already extremely wasteful and reducing laundry is necessary. If towels are left out, they will be used. I don't want to encourage such usage. I also see this from many European guests: families tend to share towels with their kids and tell me which towels have not been used (everything left out gets washed anyways). Many don't shower every day. And except from one European group everyone knows to hang their towel to dry after use.
Others expect free reign on my towels. But when I tell them to hang them they often thank me for learning them to be more conscious about energy saving. Of course I don't deny them towels. I have plenty. I just nicely hang my own towel to dry when I understand that they are oblivious and careless, speak around it and they are learning something new.
I also don't have a dryer. Everything is air drying on a rack, over doors (duvet covers and stretchy sheets) and chairs in my shared home when it's raining. Which it does between 230 and 280 days every year here... And I won't hang all this when having guests. They get the tidy home-version.
But on the good days I have i big drying rack in the garden. So I try to dry all the Airbnb fabric in the sun, giving me actual laundry-days. 😊