When farmers turned to mechanized milking at the beginning of the 20th century, some of the small farms got bigger, and production increased.
Here's the thing. Refrigeration didn't exist yet, unless you count the very ancient icebox, which you shouldn't. The icebox cost a lot to maintain and was inefficient -- because, as the name implies, it was basically an insulated box you put ice in, and ice tends to melt. And: glass doesn't insulate well.