Alright, so the argument against it is simply aesthetic bullshit (screwdrivers are okay, actually) but I can defend this on the grounds of pairing juice with champagne/prosecco makes the resulting mix tastier with the oj adding body while the bubbly cuts the sweetness and adds more fruitiness, whereas juice and vodka is adding the (extremely subtle) flavors of vodka to sweetened juice and as a result you get boozy OJ or orange-flavored booze, and it doesn't balance as well - if you want hard liquor in a breakfast drink it's Bloody Marys or Irish Coffee all the way.

That said I cracked a PBR at 8AM today.