Back in the mists of time the human form was venerated when depicted in stone or on canvas or as a fresco on a wall. Those regarding it would see the representation of a naked body as a tribute to its creator, be that a divine god, the earth spirits or some other natural force.
When people look at images, or sculptures of naked people they see the rude bits. No matter how well executed a piece of art is if it’s got naughty bits they form an intrinsic part of its appeal.
Whether we choose to recognise that, even tacitly, is a matter of fashion and the morals of the day. In 18th century England wealthy patrons may have wanted to be portrayed as cultured and appreciative of art, but that was a thin veil to disguise the real reason for all the carefully posed nudes in country houses. They are very large, expensive porn mags. If you wanted a portable version then you could have some naughty woodcuts printed.
The 19th century took the whole erotica and pornography underground and by doing so relieved it of its artistic pretensions to some degree. Combined with mass production and the development of practical photography this lead to the erotic art and porn we have today being available to anyone who wants it. Of course the Victorians would never admit to this being a society with a respectable façade to maintain to the empire, but underneath …
Erotica and Porn have been in and out of the closet for years. Now it looks like they’re out, but if censorship kicks in they now have the perfect place to hide, the Internet. I think they’re out for good.