The thought of someone giving their kid a bottle of lambic for their 21st birthday is hilarious to me. I always picture the popular kids getting new cars, trips to Europe, etc and then the lonely child of a neckbeard gets stuck with a 2015 Cantillon Kriek. I guess it's symbolic in a way; you're letting your kids down one last time before they move out for good.
I'm sure I'll disappoint my future kids in a plethora of ways, but giving them a bottle of lambic as a present on their 21st birthday is one that even I know to avoid