Sitting on something in the nude is not going to transmit anything to anyone else Eli, unless those persons are themselves nude. If this were a major vector for disease transmission we would hear more about people catching stuff from sitting on public toilet seats, which I don't think is generally believed to be a major public health issue by people who study such things. Park benches and like public seating are generally understood to be surfaces that you don't lick, or eat off of, and those who choose to disregard these norms do so at their own risk, which is as it should be.
Casual touching of surfaces with your anus or genitals that others have touched with their anuses or genitals just doesn't present a great risk under normal circumstances, and any ultra-precautious folks concerned about their mere clothing touching such surfaces could readily put down a towel or something before sitting, if they desire to sit there in the first place. A society with more public nudity could even have disposable protective covers available near public seating for this purpose if there were much demand for them, as is not infrequently the case in public restrooms where they have those paper things you can use to cover toilet seats. Not that guaranteeing the availability of public seating seems to be much of a priority for many people in other respects now. Go to a BART station for example, and look at the insufficient amount of places to sit down without sitting on the station floor (as I've often done for lack of a better seat).
The hygienic issue is a fig leaf anyway – pun intended. Adam and Eve didn't put on fig leaves out of a concern for sanitation. I think most people will acknowledge that the real issue is some people's aversion to looking at nudity, and/or claim that seeing it is harmful to children (a proposition that makes no sense in evolutionary terms). I believe these things are rooted in irrational fear and discomfort about sexuality, due to cultural and in many places personal, baggage.
I'm happy to answer your question about drinking and driving, but need you to define "drunk".
Love & Liberty,
((( starchild )))