I just tend to like the way that certain piercings look (eyebrow, labret, nose, etc), and I see it as another way to wear jewelry and express my tastes.
I finally took the plunge in July and had my eyebrow pierced, and I absolutely love the way that it looks on me. I can wear anything from a black titanium curved barbell with spiked ends (that really stands out), to a surgical steel curved barbell with light pink ball ends (that you can barely see). I have a clear plastic spacer for the piercing, but I can't get the end of it to go on (it's just an o-ring that pops onto the end), and I have no reason to wear it anyway. The piercing didn't hurt at all; it was just a very "different" experience, but not bad or painful.
The next piercing that I get will probably be my bellybutton. I love all of the cute jewelry that you can get for bellybutton piercings; I want to get a dangly Playboy bunny barbell. I don't know if I'll ever get some of the other piercings that I like the look of, but I've considered getting my nose, lip, and labret pierced as well. I would only wear a tiny stud in those piercings, if I ever get them done. I would like to get a few more piercings in ear cartilage eventually as well.
As of this moment, I have my eyebrow pierced, the cartilage of my right ear, three holes in my right earlobe, and two holes in my left earlobe. I'm 23.
This is what I tend to look like on a regular day. Here you can see my eyebrow piercing, my cartilage piercing, and a Tinker Bell stud in one of my earlobe piercings (it's blurry so you can't tell, but yes, it's Tinker Bell):