If you mean as a Vegan they are classed as an animal products, both egg and milk. The vegans have their own values as why they allow them or not, so do, some don't. I think it is very much like a parent when they say to you when you ask, "Why can't I do this, or that ?" with "Because I said so". It seem so completely illogical, as if they are deciding for themselves what they can eat or not. In some cases of the world, and I am thinking of India in particular where there are religious reasons why there are some foods you are not allowed to eat.