...when I was young, broke, and didn't have a lot of other options. But I never minded it--I never had ethical hangups about being a "whore," "slut," etc. I loved the attention and the fact that there is never a dull moment in this business. It ended up suiting my temperament really well... which is why I've stuck around so long (even though, as some have probably noticed, I take extended breaks as I need them).
I've met so many unique, interesting people, and I've learned how to feel confident and powerful in my own body. This job helped me stop caring so much what other people thought of me. Not to mention all the real-life skills I've picked up along the way (marketing, web design, conflict resolution...). Also not to mention that I love making other people feel sexy and good about themselves.
And the money, of course.

This job essentially put me through college, and now through grad school, and I have a lot more free time than friends who work 40+ hours a week just to scrape by.