To answer Shado as Jirachan forgot a question:
It wasn't just one person, it was a whole group of people. Back in ancient times people would fuck infront of everyone and a few people got the sudden urge to mate while watching others. As culture got more refined, people began mating in private, but those individuals that still needed to watch others lived on and needed a new way to satisfy their lust. Therefore they began asking some not so shy people to have sex in front of them for pleassure. Eventually, people realized they could make a profit off of this and so was born the porn industry.
What I just said was a load of BS, but did you believe it?