I do it for money, but that's an afterthought. What I personally enjoy is trying different products on different cars and seeing what kind of results I can get. Kind of a mystery, you know? I've always been a materialistic guy.
The other part I love is the reactions from customers I get. Every time I get a new customer, I have a chance to show them an entirely new realm of quailty car cleaning. Just about everything we Autopians do in our regimens most people haven't heard of. The satisfaction I get knowing that I got someone to raise their standards for car care is just awesome. And on top of it, they use me exclusively!
I'm not going to lie, when it comes to my own car, I lose some interest in detailing. I keep it clean, but I find it boring having to labor over something I see everyday. What I like about detailing is exploring different cars, products, techniques, and the unique challenges each provide.