Actually, being drunk, at least in the group of my clisest friends, has always been considered lame and even low-class. These are people I've known for over 30 years, so it's not recent.

I do think one reason why people are preferring sobriety now is that it's just plain too expensive to go to a bar and buy enough cocktails to get drunk when they can cost $12-$14 a drink. I order alcohol at restaurants, for example, much less often now.