Why?

I have been working through a weight loss workbook. One of the questions posed was, "Why did you start?" I have thought about it for a full 24 hours and still don't have an exact answer.  I remember my first attempt at weight loss was when I was six. I remember another attempt at eight. I am guessing those attempts were to be more like my little friends. In high school I made another attempt. That one was probably again more for vanity and to avoid being teased at school.  I didn't seriously attempt weight loss again until a few months before our wedding.  Even then, I only vaguely remember thinking that all brides try to lose weight before their wedding. It was as common as getting a tan, having your hair done, etc.  So, I lost 20 pounds. 
Somewhere during that initial phase of losing 20 pounds, my husband's grandfather was on his death bed. He had lost his wife a few years earlier and thought (rightly so) that many of her health issues were weight related.  I promised him days before he died that I would do everything I could to improve my health and my husband's.  Grandpa didn't want our hearts to feel the heartbreak his had. The promise I made him has been a factor that has fit into the equation ever since.
I thinking the "why" behind my weight loss is just as much about that questionn as it is about the "why not". I don't really see any negative impact from losing weight.  I guess the worst part has been having to buy new clothes. You have to buy new clothes periodically anyway though, so it might as well be a smaller size. I don't notice an impact on our grocery bill.  The cost to eat healthy has cost about the same as what it cost us to eat junk food.  I would like to mention that I think weight loss is like an insurance policy of sorts.  I am making an investment now, that in the future will reap many benefits. For example, I pay a monthly fee for my weight loss program.  Someone asked me if I minded spending as much as I do. No, of course I don't. Even if it costs me $1 a day, that would be roughly $365. A single trip to the doctor for an obesity related illness is going to cost more than that. Surgery? Yeah, that will cost triple (with good insurance). 
So I guess the answer to my why is another question, "Why not?"