I have been a vegan by choice for six years and never stumbled over a vegan adult in need of protein supplements.
FYI: Germanys strongest man (Patrick Baboumian) is vegan ...
http://tophealthnews.net/one-of-the-strongest-men-in-the-world-is-also-a-vegan/
It is mainly to assist in fueling recovery from my workouts. I am no cardio bunny. I prefer heavy weights. =)