If you care that cows only express milk after birth and thus the industry is a combination of forced pregnancy and infanticide (most calves aren't economical), that's a long-winded way of saying "milk is immoral", and people quite often go from "$thing is immoral" to "I will not purchase $thing".
* Or at least, can be non-vegan: there's bacterial sources of casein but I don't know how economically relevant that is.
https://en.wikipedia.org/wiki/Milk_fiber
If you care that cows only express milk after birth and thus the industry is a combination of forced pregnancy and infanticide (most calves aren't economical), that's a long-winded way of saying "milk is immoral", and people quite often go from "$thing is immoral" to "I will not purchase $thing".
* Or at least, can be non-vegan: there's bacterial sources of casein but I don't know how economically relevant that is.