I am not sure if science as we understand it had so much to do with it.

To my experience, society changed enough to no longer tolerate--or at least accept as normal- drunken family members. There was a point where the always-drunken-grandfather was suddenly considered ill and no longer just a little weird. A noticed this in my own family when I was still young. There was a point where constant-drunkenness was suddenly frowned upon with a certain vigor. And the younger generation sort of got the message: "I dont want to be like grandpa, he is actually a poor devil..."