I think @Richard Y Chappell🔸 is right. I'd add that lots of my non-EA peers care about hypocrisy (ie, they would be unwilling to entertain arguments in favour of veganism or donating to animal welfare coming from a non-vegan). 

I care a lot about spreading the cause of veganism (and effective altruism more generally), and I think that by eating vegan I hold a certain amount of moral legitimacy in the eyes of others that I don't want to give up because it might help me convince them about animal welfare or EA one day. (Being vegan also provides some reflective moral legitimacy or satisfaction to the irrational part of me that also cares about hypocrisy.)