It wasn't an issue until dairies started turning into factories to supply growing cities, with cows crowded inside and the manure concentrated in one place whic

It wasn't an issue until dairies started turning into factories to supply growing cities, with cows crowded inside and the manure concentrated in one place which encourages the growth of pathogens, and low-wage employees who weren't necessarily as careful about keeping the cows healthy and manure out of the milk as a traditional "dairy maid" might have been. So the industry had a choice: go back to keeping cows on pasture, which would mean the expense of transporting the milk further into the city from distant farms, or use the new technology of pasteurization to kill all life in the milk, good or bad. As always, industry went with the cheaper option. Which is fine; I wouldn't drink raw milk off the grocery shelf if I thought it came from a large factory dairy. Milk produced that way should be pasteurized. But it wasn't necessary to criminalize doing it the other way. That's just an industry trying to protect itself from competition. If your raw milk comes from cows on pasture, milked by people who make an effort to keep the cows healthy and the milk clean, there's nothing to worry about.