We need to drink milk.
This is not true.
The NHS, the British Dietetic Association, the America Dietetics Association and the Academy of Nutrition and Dietetics all say you can be a healthy Vegan at every stage of life. Here is a free PDF to download that includes the information from all these world health bodies - https://tinyurl.com/y5fzl3vk .
To learn about all the dangers of eating animal products check out this page Vegan For Health.
The majority of the world are lactose intolerant, so they don't need to drink milk.