I’ve heard so many reasons why people have started martial arts:
1) Exercise - Its how I got started.  Got bored of going to the gym and wanted to supplement my workouts. I took my first class and could barely move the next day without pain.I knew that was what I wanted to become my workout from there on.

2) Media - There is a little girl at my school who started training because she saw a cartoon whose main character (a female main character) did Karate. She comes in last week and goes and someone askes her about the cartoon.  She replies with something to the effect of “She won’t be as good as me.”

3) Discipline - Lots of parents start their children in Martial Arts classes so they can learn discipline. Sometimes it works, sometimes it doesn’t. The main focus in these cases, it is for the child to learn to listen, take criticism, and learn to communicate better.

4) Deficiencies - In recent times, with the successes of medical and scientific findings, we can test people and see what they may be deficient in.  It might be mental or physical coordination, but these can all be improved by practicing activities that strengthen these characteristics.

5) It’s Cool - I mean it really is.  Being able to throw kicks, break boards/bricks/concrete. Se’ve seen it for years, people doing quasi-extreme things that baffle and impress us.

I’m sure there are lots more, but that is all I can think of for now.