What's your health worth to you? Seems like a simple question, but few answer that question with a lot of thought. A simple answer is, "I want to be healthier." I would assume that most people want to be heathier, but then they turn around and have a pizza and regular soda for dinner.
Some more well thought out answers would be...
"My health is worth watching my children grow up."
"My health is worth leading a functional life now and when I am older."
"My health is worth being able to enjoy the physical aspects of life."
"My health is worth not having to take additional daily medications."
The short answer isn't specific. There isn't one thing that can be singled out and then drawn on as a negative if they don't choose to be healthy, at least not in relation to their life because we don't know what drives them.
In the last four answers, there is a constant reminder of not being able to see your children grow up, having to rely on others to do daily tasks and to get around, not being able to enjoy activities, or having to take medications. The last four answers give you a driving point a specific reason for working out and following proper nutrition.
The deeper you dig for an answer the more you find, the more you have to work toward, and the more reason you have to succeed. Generally speaking one thing always leads to another. Usually the first reason is more vague and the later reasons become more specific.