I’ll be a good sport and take this in stride.
First, how does bodybuilding “ruin your health”? Aside from steroid use (and then only in obscene amounts, such as those used in the pros) all aspects of bodybuilding are healthy.
Most bodybuilders I know eat cleanly, do not drink, smoke, or do any drugs--certainly not regularly, at least (ko and Patrcia's love of beer aside)--and obviously they exercise regularly. All of these are very healthy characteristics.
I certainly hope you're not talking about "excessive" protein intake, because most research would prove that such a concern is silly. Supplements, used correctly and in appropriate amounts, are not at all dangerous.
As far as focusing on something "more important"...who says we don't? Bodybuidling is really not a career to the majority of the people on this board. It's a lifestyle, yes, but one which does not at all take away from other "more important things." Bodybuilding comes with a certain amount of discipline that often has carryover to most other aspects of life.
Most of the people on this forum are either in school, or have graduated college, so you have education covered. Additionally, most of us take this seriously, and it is an educational process. We constantly seek to learn more so that we can continue to improve. I happen to feel that improving your body through training is as impressive and worthwhile as improving your mind through education. The great thing about bodybuilding is that you get to do both.
You mention "getting rich" but I think it's a fairly obvious fact that money does not equate to anything other than money. If your definition of a person's worth is determined either by the number of degree's on their wall or the amount of money in their bank account, then perhaps it is you that you need to examine, not us.
I happen to feel that personal fulfillment, self-esteem, etc are more important than money, but by no means do they feed you. I feel it is important to be able to support yourself and those around you, but being "rich" is a relative term. Who wants to be a fat, miserable millionaire? Certainly not I.
To answer your question on a personal level, I seek to improve my body for several reasons. I like the way it makes me feel. I like the way it makes me look. I like the way it makes me feel about the way I look.
I like setting goals for myself and commiting to them, and then, finally accomplishing them. I like the fact that my body is truly MINE to control, and that through manipulation of diet and training I can change it if I do not like something. I like that I know enough to realize that I do not have to be resigned to filling my body with all sorts of crap that will make me look and feel terrible. I like that it gives me confidence.
I don't know that this answers your question, and I know that I do not fully speak for everyone hear, but I would like to think I've given you a little insight.
Hope this helps.