This wasn't predominant in rural areas; it became necessary in cities/towns where sewage wasn't kept out of drinking water sources. If your water is unsafe, beer or ale becomes your standard beverage (except when the water is boiled, e.g. for tea or coffee).

>the past couple decades.

Well, Islam has forbidden alcoholic drinks from the very beginning so that means you are off by at least 1400 years.

Children drinking alcohol?

Yes, absolutely. Not much, granted, but if you look into the history of beer production, you'll see commonly the production from a single mash two, or even three beers, ending with the "small beer", which was commonly served to all, including children. Because wort was boiled, it was a safer alternative to water, from a time before germ theory was understood.

Ok. But not even close to the way kids drink sugary drinks today.