Having been social nudists for over 23 years and understanding etiquette of sitting on towels at clubs, resorts and other nudist's homes, we continue to use towels even here at home and have for all that time. Before that, during the 20 years of home and backyard nudism, we used sheets, blankets and even towels to sit on but never realized it was nudist etiquette.
We have extra towels for quests, whether they are nudists coming to visit or textile friends coming to use our pool and hot tub. Each time we invite friends or family over, we always let them know that we have towels for them to use.
Yes and no.
If going to someone else's house, then absolutely- bring and use towels. That is the social protocol.
When it's just wife and me at home, unless we just got home from work, we don't use towels. We usually shower as soon as we get home (outdoor shower has paid for itself hundreds of times over!) and are clean. Rule #1- Clean your butt! If you do a #2, then shower and clean your butt. Simple! You won't leave any residue where you sit.
When nudist friends are coming over, we just grab a stack of towels and leave them on the arm of a couch and then they can grab one if they wish. We do insist that company use towels, and as a courtesy, we do also when company is over.
If you are leaving 'marks' behind, then you are not cleaning yourself properly. I was raised with a nudist family, and mom was always very persistent in making sure we cleaned ourselves properly. FYI- wiping your butt with toilet paper isn't enough. For example, if you got poo on your arm and wiped it with TP, is it clean? Of course not! Soap and water are required.
I do believe it about personal hygiene. Body oils can soil fabrics and I believe that even as clean as we can be there is a good use to sitting on a towel. Especially in someone else's home or back yard. I keep my body very clean and don't feel a bit uncomfortable about sitting on a couch or chair nude, but we never know. So I just like to be considerate.
Interesting conversation and one of the biggest concerns from the textile crowd. There seems to be two different takes on this and the answer appears to be a combination of keeping your butt clean and using a towel where necessary. I am a fastidious clean freak body wise and I think most nudist would be more in tuned to the cleanliness of their bottom side. (I haven't left a skid mark since I was potty trained.) I also agree with Carla about body oils and fabrics. Most of my furniture is leather so the answer is "it depends". If you have a nude guest, then yes by all means, offer a towel for your peace of mind as well as theirs. You know the condition of your bottom, you don't know the condition of theirs.
It depends on the person and the setting - some people "leak" more than others, and it's often circumstantial. The towel rule is clearly a good general practice, but I don't treat it as a hard and fast rule at home including for my friends, but the places I sit regularly have something easily washable in place.