Ehhh...my reason: quantitative decision making, and lots of it. It's the most wonderful game (in the mathematical sense of the word), and playing (and more importantly, being successful) is its own intrinsic reward.
And yes, models are nice. So long as you know the assumptions behind them, their limitations, and when you need to adjust for any inaccuracies.
The rewards come later with success. Become successful, and the rewards follow.