My friend gave me a milk box they snatched from a highschool. My 24yo ass drank that box in the middle of New York happily. Tickled a core memory. No one cared.
This! The reason milk isn't "socially acceptable" to drink around in public is because milk isn't really something that is commonly in a portable form factor. If you see someone drinking a milk carton in public it's no different than seeing someone drink a juice box or a can of soda, or a can of beer. Except milk cartons aren't really too commonly available at any gas station.