And why did they all avoid drinking water?
Europeans and Americans would only drink water that was cooked in some way. There was no basic sanitation in those times for people or livestock, and certainly no water purification plants. So the water was likely to be potentially contaminated with any number of a thousand different kinds of diseases.
I read something a while ago which said that Vikings drank mostly beer. Germany, of course, is known for beer. And France is known for drinking wine all the time all day long. These customs originated because these fermented drinks were safer than drinking the water. Also, according to what I have read, the alcohol content was much lower back then than it is today. And that makes perfect sense. If you are drinking something to quench a thirst, you would want it to have a low alcohol content.
In summary, wine/beer/coffee was like water to those people. In fact the word Whiskey means 'the water of life'. And vodka in Slavic means 'little water'. But again, the alcohol content then was not like it is today. It was meant for drinking like we drink a soda pop today.