I do it because my life is boring and I need something to do when reruns of West Wing arn't on.
Truly for the following reasons (in no particular order):
I looked in the miror and did not like what I saw.
I wasn't strong enough to do something I wanted to.
I lost an arm wrestling competition to my brother.
My wife said I was fat.
I noticed a "double chin" thing.
I got winded playing ball with my friends.
I went to work for my dad (construction) and it was difficult.
I hate asking for help, and kept having to for heavy stuff.
I like to challenge myself.
I wanted to be as good looking as I am smart.
I've never had a slim stomach.
It scares me to think, by the time I have kids I won't be able to play with them.
Some of my friends were doing it, and I'm extremely competetive.
I made a promise to myself.
I'm sure there's more, but those are clearly the most important.