It's pretty much about what they are competing with, it seems? Those are leisure routes and they are mostly competing with LCCs and 'legacy' airlines with BoB (buy on board) service in Y like BA. They have no incentive to offer free alcoholic drinks in Y when their competitors are offering essentially nothing (not even soft drinks) for free.
Not that I'm saying it should be liked, but I'm just saying that I can see why they do that.