Don't leave your towel on the hotel floor

My boyfriend and I were on holiday last week and here in Europe a lot of hotels have a sign in the bathroom which says to only lay the towels on certain places where the workers know that they need to was them if you really don't use them. And we always use the towels as long as possible and only give them away when they are dirty or smell. We also try to don't leave a big mess so they don't need to work very hard.