Thanks again for all the answers. So many replies in just six hours, wow.
Basically it boils down to stark cultural differences, apparently. General tendency of all answers is that it seems to be mainly an American thing, which is funny as they are the world's biggest porn producers and most sex story sites are hosted in Americaland as well. Guess it's the forbidden fruit thing.
To give people an idea why it astonishes me so much. It might not be our public image, but us Germans are quite liberal in that regard. It's not uncommon to come across a topless female in a movie or TV show shown late afternoon. If a movie features full frontal nudity but no explicit or implied sexual activity, it gets an FSK16 rating, which means it is open to people from age 16 and over.
It's even more liberal in East Germany. The former communist regime actively supported nudism and there are a lot of nude beaches and even nudist camping sites. As hinted in my Story "Learning To Live In A Strange Land", the joke among us was that the regime supported it because it enabled them to sell all the swimsuits and Bikinis to the west for much needed hard currency.
I practically grew up on nude beaches, so I guess I'm just a lot more relaxed about such things than many other people.