Orient Land trust curiously had no towel rules that usually go with naturist resorts. DF and I tend to sit on towels to protect ourselves. When car camping and bathing is difficult we use sit-down towels for ourselves in our own chairs. In the sweat, we use small sit-down towels. Others just swash water over the wooden seats before sitting.
OLT is my long time preferred CO resort. They really don't care much for rules. I like that. There are plenty of showers and soaking pools to make people clean all over.
The old sauna at OLT was small and had an upper shelf for someone who wanted more heat. It was close to the roof so one had to lie down on it. Often sweat would rain down on the people sitting below. They replaced the old sauna with a new fancy one.
I have provided large towels to sit on for guest in my home in the past. Sitting here on my couch infront of the computer, I always have a large towel across it. It washes and cleans easier than furniture. There are sitting towels all around the house. If I'm not recently cleaned as in showered, bathed, etc., I forgo the towel. Being in warm water as much as out of it at OLT, sit-down bacteria didn't give any concern.
I don't use or provide sitting towels at home. I really believe its prefereable for people to be washed and clean rather than sitting an unwashed behind on a towel.
As for being polite, or considerate. I don't consider wearing pants an act of consideration, it in fact often makes those of us uncomfortable when people wear pants around nudes, depending on how well I know them and the situation.
I'm not sure that insisting someone sit on a towel is being polite. It has overtones of "You're too dirty. Don't touch anything." That seems kind of rude to me.
Experience has shown me that bare sweaty bodies do leave dirty oils which influence the lifetime of cloth furniture, which certainly includes topfree people. In Arizona heat, it is best to practice these courtesies, unless it is a bathing together situation.
Leaving sweat on cloth seats would be a problem, but not so on vinyl, metal, or wood seating. I sometimes cover my vinyl chair with a towel when I come in sweaty, as much for my back as my seat.
My grandmother had fitted white protective covers for the arms and head rest of her fabric chairs. It kept skin oil from hands and heads from staining the fabric. Such covers were pretty standard in her day.
