Not sure why it's treated as a joke as sex is an important part of a healthy and balanced lifestyle for most.
Sex is nice and pleasure is good for you, but it gets treated as a joke because people are embarassed to talk about it, even in long term relationships.
This means that very many people don't actually have the kind of sex and intimacy that they really want. And when it comes to trying to negotiate with your partner to get the kind of intimacy you want, people get tongue-tired and awkward, especially women, because nice girls don't ask. Although how anyone can possibly bring pleasure to a partner without knowing what turns them on is beyond me. Hardly surprising that the libido hits rock bottom.
The biggest erogenous zone you have is in the space between your ears, if someone can't stimulate that part for me it really isn't going to go anywhere else. There is so much more to intimacy and a healthy sex life than penetrative sex, which is where many discussions seem to start and end, often with bruised egos.
Now, while there can be huge thrill to an illicit quicky, I'd say most of us would like to spend a bit more time. I think you need a running buffet attitude rather than a fast food approach to good sex.