I don't think it's immature.
I don't drink, and since I stopped there's a whole new universe of alcoholic beverages I know nothing about. I wouldn't know where to start.
Alcohol is really expensive, and, for me, what would I do with the leftovers? Or if you drink, what if you're stuck with stuff you don't like?
Give it away to the last people leaving the party?
I dunno, unless your Mrs. Gotrocks your friends are going to understand it's expensive to do the whole 9 yards....and if some of your guests are family, well, damn, bring your own booze cuz....
Anyway, when I go to someone home for a gathering, I never go empty handed. I always bring a gift of at least flowers, or a small box of good chocolates, or in this case, a bottle of wine or whatever.
If my friends don't like BYOB, they're not my friends.