I'm onboard with all of the reasons.
I've noticed that most vegans are vegans and the vegans who stay vegans do so because they don't want to hurt animals.
Environmentalists tend toward reducing their animal product use rather than eliminating it.
Health nuts tend not to have a problem with taking in moderate amounts of animal products occasionally unless they are the type of health nut to identify with and base their self esteem on a special diet.
Are these statistical facts ? I don't know if you can generalize.
At least here, I actually see many that do it for Ethical reasons. But they are still stuck in their old beliefs regarding what's healthy and what not. Or they don't care about making their Nutrition healthy enough. They just remove animal products and eat Vegan junk. Without including enough replacements or eating healthy Vegan Diet. So it makes them blame Vegan nutrition and sometimes break or go back to an "easier" Vegetarian Diet.
Ok I'm busted. I'm one of those people who tried to go vegan after but ended up going back to that "easier" vegertarian diet.
But seriously I am a vegetarian/almost vegan for a health reasons as well as consideration for animals. I don't eat eggs or milk straight however I may cheat and eat non vegan foods like the subway veggie max, the bk veggie burger or donuts made with milk. I am not perfect but I am always stiving for perfection in my diet, lifestyle and walk with God.