Do I "need" a drink? No. Do I think it enhances certain elements of my trip- most definitely. I mean, I "need" it about as much as I need another trip to WDW.
On top of that, there's a significant difference between enjoying a drink for the flavor of the drink or the pairings involved vs. drinking to get drunk. Even the one time we drank around the world (and got a bit tipsy), we were not slobbering drunks and were doing it to appreciate different offerings from each country in the WS. Ultimately, I think that's the area of WDW that really benefits from the drinks...i.e. it merely adds to the depth of the experience from that specific country. I don't drink much at home, but on vacation it's just a nice treat.