"Tradition. There's a whole cultural thing about wine, it almost is like a parallel to fashion in its way - people judge your wealth and your aesthetics by what drinks you serve with what at what occasions. And there's a cultural language surrounding other alcoholic beverages, too, wine is just the most complicated subcategory. Like, Vorkosigan District maple mead is famously a poor rural beverage, you'd never serve it at a high-class gathering like the Linya Doesn't Bite Party, but in the poor rural areas of Vorkosigan District - which is most of Vorkosigan District - they serve it at their parties. If I took it into my head to bring you to Silvy Vale and introduce you to the Csuriks, you can bet there'd be maple mead involved. Providing socially appropriate forms of ethanol to your guests is a standard aspect of hospitality."