Conserving resources within the dairy industry, such as consuming the surpluss calves and cattle that are killed, might make sense from an economic standpoint.
But the dairy industry itself isn’t necessary. It matters because instead of supporting it by buying the veal and beef byproducts derived from it, we could simply boycott the whole industry entirely, which would eliminate all of the harms involved in it.
You seem to have made the exact fallacy that I’m describing in my post, as seen in the title.