I don't eat meat or any animal products.  Going vegetarian has improved my health for sure!
Some people do it just for respect of sentient life
That is the other big part of why I do it. I have seen how animals are treated and its just not right. Its so sad.
Some vegans also avoid things like beeswax
I have been learning about that.  I think bees can be cared for well but the fact is; many companies take too much from the bees.  I don't eat eggs either.
Leather and silk and even goose fat in polish is avoid
yes, I got rid of all my leather goods and am careful with my makeup and body care.  I just ended up making a lot of my body and skin care myself. 
Packaged foods and things like cakes are often outside of the diet, as well