There is a world of difference between "vegetarian" and "vegan". I raised my children vegetarian with PLENTY of milk and cheese, and they are strapping healthy adults.
The vegan diet, OTOH, is terrible and unhealthy. Cows were designed to give more milk than the calves need so people can drink it. And people were designed to drink milk.
Goat's milk is healthier, but more expensive because they're smaller than cows. Cow milk produces so much extra mucuous at least with me. I wake up coughing, it's digusting. That's why I'm getting rid of it.
Cows were BRED to do so, over thousands of years.
And people were designed to drink milk.
They were designed to drink their mother's milk, not the milk of another species. Drinking cow's milk isn't any more natural than drinking milk from a hyena or a walrus.
Many cultures do not drink animal milk at all. Most Asians are lactose intolerant as well as a good percentage of hispanics. Go to a Chinese or Japanese restaurant and you'll see nothing with milk on the menu. And some people, like the American Indians, never had cows.
Regardless of what the dairy industry would have you beleive, you do not need cow's milk to survive.