Pure ego.
The health desire is good and all, it was the reason I lost 35kg. But now its because I want to be a sexy dad, I want other dads to say "Jesus I dont know how you do it!", I want other Moms to be just a little bit jealous of my wife and I want my wife to be just a little bit worried about the thirsty ass single moms at school pickup.
I got "In shape" now it really is an exercise in vanity, and I'm ok with that.