Lots of people drank wine, beer and ales because drinking the local water would make you sick.
We take for granite now that our drinking water is safe.
This was not the case for most of the last two thousand years in many places in the world. Except ROME.
The Romans built a water and sewage system.
Slavery gets SH#T done.
One of the cool inventions of Dean Kamen was a portable machine about the size of a generator. You could transport this in the back of a car and poor dirty water through it and it would purify it.
That’s true: in the past when bad water was common and would kill you, mixing water with wine was a sensible, if not necessary, precaution. The Greeks, for instance had Kraters, large two-handles vessels, typically elaborately decorated, specifically used for mixing water with wine.