The advantage of industrial production is the ability to keep products completely clean. This is how dairy products are manufactured all over the world. The milk (and other raw materials) are pasteurized (heated to a high temperature), which ensures the product's microbial cleanliness.
From the moment the product is pasteurized it is no longer exposed to the outside air, which guarantees its absolute cleanliness when it is packaged. The product stays this way until it is opened.