lemuria: Try the raw food diet, it's a great experience and it will make you more aware of the effect food really has on us. Also, good luck on the polyphasic, I just started myself and the first week is a real challenge.
KeithS: If there are exceptions, then you really can't say "Never."
I think you don't know enough real vegans yourself, being a carnivore and all, but they are out there. For the figures though, only about 3-7% of people consider themselve vegetarian, based on polls, and only about 0.5% of people are vegan. That means you would have to know 200 people and their eating habits before you knew a vegan.
Lastly: When I see people around, I notice that not all of them look healthy. I would say less than half. That's a staggering number of people being unhealthy on the regular diet. I believe that until we can find the one perfect diet, we'll still be searching.