Veganism can act as cover for disordered eating; perhaps that is what you have observed.
Related, I know many “vegetarians” who are what I call effective vegans, meaning they eat vegan ~90% of the time, recognizing purity as a pointless pursuit.
Anecdotally, vegetarian seem to eat a lot of eggs, fish, etc. Yes I know fish is technically not vegetarian, but.. they call themselves vegetarian and certainly avoid other meats.
Just saying, my experience with vegans is very limited. For all you know, the vegans you know are, in fact, cancer patients. Cancer patients are much less rare than vegans after all. Not everyone tells the people around them.
Related, I know many “vegetarians” who are what I call effective vegans, meaning they eat vegan ~90% of the time, recognizing purity as a pointless pursuit.