Without milk you won't have butter, mascarpone, cream, cheese and yogurt (and many spreads).
Milk is also the basis of most breakfasts around here, with granola and other cereals. We also give milk to children in school to help those that are poor and may not be eating properly at home.
On a lighter note, milk is essential for the confection of many cakes, for chocolate, ice cream, as well as for many recipes, sweet and sour.
Today, too, dairy is an important aspect of many cultures.
> Sandra Ott’s fascinating ethnography of Basque shepherds (Ott 1981) reveals much about the central role cheese can have in everyday life. In the remote French Basque Pyrenean village of Sainte-Engrâce, the cheeses that local syndicates of shepherds produce from their mountain huts takes so much care and attention that the resulting product is treated both metaphorically and ritually as their “children”. The formation of both babies and mountain cheeses alike are seen as analogous processes in the local worldview: “men’s generative creativity in procreation as in cheesemaking is believed to convey not only form but also identity. Basque cheeses, no less than children, have paternity and come from patrilineages (Paxson 2013: 52)”.
https://hraf.yale.edu/the-social-life-of-cheese/
Dairy products aren't just food. They're millenia old culture and identity.
So people aren't allowed to change their preferences or way of life if it's deemed "cultural"?
However, saying "cow milk is for baby cows" is a silly reductive take that ignores pretty much the entirety of human history and the heritage we've built around it.
Oat grains are for baby oat plants! - See how silly that sounds?