"Why do you do it?"
People always ask me that, like maybe there must be some single reason.
I always say, "For every reason you can think of, and maybe some you didn't."
By every reason, I mean there isn't any reason to eat animal products.    The reasons for being vegan
encompass everything.   Finally I am vegan because I can be.  Because it's possible.  Because, why not do it if it's possible.  The potential health benefits are reason enough alone.  

Animal Rights ***
Environment   **
Health *
Benefiting people .
Economy
Ethics
Spirituality
(Possibly) Preventing Mad Human Disease (CJD).
(Possibly)Preventing Alzheimers
Helping people who want and need to lose weight.
Fighting the industries that would keep America fat.
Food safety .
Something to be passionate about, something to do.
Advocacy .
Can never go back .
Just because .
 

Sure, only one thing caused me to become vegan in the first place:  reading Diet for a New America.   But it presents multiple reasons.  That's one reason why it's so effective.  That was seven years ago.  Now John Robbins has written another excellent book:  The Food Revolution.