Why own a guitar if you are not going join a band?
Why buy adobe photoshop if you are not planing on making graphic art your career?
Why jog every day if you are not training for a marathon?
etc
etc
etc!
A lot of things we do that really make no sense, i know a ton of guys that get together and play football, baseball, basketball, and will never play professionally, and don't want to. Maybe not a proper comparison, but to some it makes no sense to play basketball every day at the park, if you are never planing on doing it as a profession. I mean why hit the gym 4-6 days a week if you are never getting on that stage? We do it, or we use it, because it's another boost to get what, or where we want! Not every one is blessed enough to get ripped through diet, and exercise. Yes diet and exercise will lead to a better you, but it wont make you as shredded as the guy next to you, with the better genetics.
I know plenty of females for example that bust their ass in the gym, eat properly, and try their best to be as healthy as possible. Yet these same women still have areas that just do not seem to improve much, if at all. Meanwhile females with great genetics just look at a gym, and have great physiques. So should these females not use something that could help them, if they are not stepping on that stage? I would say any adult should use, or do what ever he/she feels is right, to achieve their goal. Also consider that a diet aid, for some may be of much less of a risk, than the excess weight they are carrying. JM2C