There are different breeds. Jerseys give high fat content milk (yum). Holsteins give a lot of milk ($). Angus don’t have such great milk. Etc. I don’t know all the breeds, but you get the idea.
So, yeah, most of the males end up as veal, but some of them have to grow up enough to impregnate cows with the right DNA, so the next generation of cows give the expected kind/volume of milk.
