), most people do it because they don't want to support the unethical treatment and exploitation of animals. Couple that with the fact that meat is isn't necessary in a healthy diet (Why kill animals when it isn't necessary?) and there you go. Vegans take it a step further...
PS OP you should watch the documentary "Forks Over Knives" if you're actually interested about the subject. The documentary dispels a lot of the misinformation out there in a non-sensationalist way, while answering tons of questions I'm sure you have. I've seen it probably ten times now after showing it to various family and friends. My aunt decided to completely change her lifestyle and diet after seeing it, got fit and lost 60 lbs, so that's a testament if anything is..Anyways I think Netflix has it, if not, torrents.
Besides those that do it for a false sense of nobility or to follow the trend ("I care, man."
You, and a surprising amount of people miss the point. You include health benefits as barely an aside, as if it's only a minor consideration for most people. In fact, I think you'll find that it's much less about "nobility" (what?) or some sense of superiority or even a moral obligation, but more so about feeling healthier and more energetic. It's really not as extreme as you might think..
Come now. Nobility...as in they're taking up a noble cause. 
