Ah but that is just it, in Heinlein's worlds the nudity may be unremarkable, but then so was the incest, etc. And they were always very much linked... Example. Over the course of a few pages you encounter a family where nudity is the norm, leading to a boy asking a girl what the difference is between the two of them (girls parts being mostly out of sight), leading to the mother suggesting she spread her legs and show him ("wink at him with it"), leading to incest, leading to whole huge orgies of incest and time-travelers taking huge risks for the sake of incest. Believe me, neither Heinlein nor his readers were meant to miss the idea.