Why does sex involve poop?

For most people sex does not involve poop.

Normal sexual intercourse has nothing to do with poop.

There are groups of people who like to do things during sex that would considered strange to other groups of people.

Anal sex involved putting your penis in someone's rectum. The receiver should cleanse his anal area throughly before doing this, so that no poop is involved.

Another more disturbing (to me) event is: Coprophilia. (see related link below)