The beer that Europeans started drinking hundreds of years ago was first brewed because They didn't know how to properly dig wells, keep them sanitary etc.
Their johns, garbage dumps, etc. would leak into the water table and contaminate large amounts of the drinking water for towns or cities. They were frantic to find a way to clean their water, quickly and in large quantities. They eventually found that if you crushed hops, put in some spices and flavorings, and let it ferment for a while, it would produce a little alcohol more quickly and easily than wine, hard liquor etc., enough to kill off a lot of the bacteria in the water. Didn't take much to passably "clean" the water, so beer was rarely made with alcohol content more than a few percent. Drink enough of it and it gave you a decent buzz too.