My first concern with my weight is my health. I want to be alive for awhile, and will probably have a better shot at it if my weight is within healthful limits. There is some serious heart and cholesterol history in my family too. Weight is something that I can control, and hopefully the other medical concerns will stay away if I eat right most of the time and exercise.
The second concern is financial. I can't afford to buy new clothes just because I grow out of the old ones. I've been fairly heavy before and had a whole gamut of sizes in my closet. It was ridiculous, expensive, and I refuse to do it again.
So yes, like Cil, I like being on the thin side. I will never forget my son commenting on a friend's truly obese mother. He said, "Mom, please don't ever look like that. It would be so embarrassing." I started eating better the next day- that was some serious motivation!