I was in the industry for over 10 years, and I never had to sleep my way into a job. Sure you get invited to a lot of parties, and some guys end up hooking up, but it's not quite the fantasy that this link suggests.
During a casting, or "go see", you do end up in your underwear so that they can see what your body looks like, but no, you do not have to have a boner, and no you do not have to go and blow someone. There was one big designer I worked for, where during the fittings, 5 of us were standing around in our undies for about 30 minutes waiting for clothes to be brought to us to try on. People kept walking by or into the room, but that's as bad as it got. It was like hanging out in swimwear.
Oh and you will have the occasional stylist who wants to "adjust" you, but you just swat their hand away and tell them that you can do that yourself.