Those are the same reasons I keep at it too.
Running into former classmates....well my experience is similar but in a different way (different age group, I am 25). I was a big geeky, quite an ugly duckling in high school. Now I am....quite the opposite and when I run into former classmates, the look on their face is worth a lot. Even better when they are guys that ignored me in highschool, who now ask for my number...and I turn them down.

But looks isn't everything...
My mom had a heart attach and almost died, and she was very healthy, it is genetic in our family, our bodies make bad cholestorol and not enough good cholestorol. Even at 25 I had a bad cholestorol test! (I am 115 lbs, 5'5" btw). So I have to work EXTRA hard to be fit. I stopped eating meat too in addition to running daily.
Sometimes, I wonder "whats the point?" to working sooooo hard. I look at friends of mine who are just naturally skinny...but there is a real big difference between those who are skinny couch-potatos and those who really work hard and are athletic, not just in body tone but skin tone and endurance.
I also have ADD, and there is quite a difference in my focus if I have been working out for a while versus if I have not. Exercise naturally keeps me focused on my work.
Lets see what else? Oh I just feel very good about myself too

Can't argue with that logic! Sure it is a lot of work but it is a better quality of life. And I have a major sweet tooth I have to satisfy, so I like that I can eat sweets (within reason...I dont eat fast food, but I love chocolate, ice cream, etc.) and still maintain a good weight.