Joh Certainly doesn't hurt now, it was 15 years ago when I got pierced. I took them out when I hit 30.
As for what I got out of it... well they were fun to play with! Running a necklace through them, feeling the vibrations through your nipples... It's yum. Licking. Pulling. Bondage. The list goes on!
Regarding the act of piercing itself... that's a tough one. It was very much a product of its time I think, so maybe fashion. An act of teenage rebellion. Mild self harm perhaps. Finding your limits. Learning about your mind and body, and what you can put up with. It's a challenge and a rush, and you are left with a little reminder of what you "achieved", for want of a better description.
Sometimes I miss them but I wouldn't do it again, i have much more respect for my body now than when I was a teenager.