Being vegan is about animal suffering and consent though
And regardless, for some, after avoiding animal products for a long time the thought of eating them can come to be unappealing.
1) Animal well-being.
2) Environmental well-being.
3) Personal health well-being.
You may substitute well-being with suffering, and there's also a nuance between death and staying alive but using (e.g. milking).
[EDIT: I suppose there's a fourth, a psychological reason how some people find certain products 'impure' to eat. But I'm not sure how I'd define that group.]