Back in the Middle Ages in Europe water was considered unhealthy. This was because it was unclean and full of harmful bacteria. For centuries dating back to the early civilisations water was made drinkable by adding alcohol, usually wine. This is why the majority of Western people carry the enzyme to digest alcohol as they’ve inherited it. If your ancestors didn’t carry this enzyme they couldn’t drink the water and died as a child.
However, the early Chinese civilisations realised that boiling the water made it safe to drink and did not need to use alcohol to make the water potable. This is why 36% of the Asian population do not carry the enzyme to digest alcohol and cannot drink wine …. poor things!