I literally just wrote about 400 words of why I love music so much, until I realised I wasn't really answering the question.

So yeah, I really really really like music and I really really really want to be part of it.

I don't think you should look at why other people do it though. I used to do this a lot, and got really demotivated because I thought I was in it for the wrong reasons, when it really doesn't matter what reasons you have (unless you're going for world domination or something, I think there's better ways than music to achieve that).