It's interesting that American attitudes towards public nudity have become more prudish while we became less religious, I find that counterintuitive.
It is maybe counterintuitive but I wonder if there isn't a connection rather than a disconnection.
In so far as secularization is connected to sexual liberation/revolution, that is. Maybe we have hard time seeing nudity in non-sexual way
because of sexual liberation rather than
despite of it.
Although there has probably always been some kinds of erotic/pornographic materials and talking and writing about sex, prostitution etc. , it nevertheless seems there was less of it and it was less public (although it varies over time and place). In addition sex itself was to a significant extend (although obviously not wholly) contained to marriage and for both religious/cultural/ideological and biological reasons strongly connected to preproduction.
Maybe all those restrictions and repressions created a conceptual space were nudity, which probably is always at least potentially erotic, could be seen as non-erotic. At least in some contexts.
Now we live in a different world. Not only is there all kinds of erotic and pornographic material widely available, in many mediums, some of them as a part of public sphere. Sex is also discussed very openly and publicly. Religious/cultural/ideological restrictions on sexuality have weakened as we have become more secular and medical technology has changed biological reality, unchaining sexual act from reproduction and making sex itself more of an erotic thing than it was before.
Basically I'm claiming that our culture is more eroticized than before and hence we are more likely to see potentially erotic things as erotic and probably see more things as potentially erotic.
Hopefully that made some kind of sense. It could also be utter bullshit but I think I'm on to something.