One of those “It seems useless now but if it wasn’t there, things would be noticeably worse” things.
Also, alot of countries that don’t have public drinking laws also are culturally more respectful of public spaces.
Genuine question: why is it illegal to drink on the street? Like, if you can chain smoke cigarettes out doors, why can’t I just sip a beer as I talk a walk through my downtown? One of the weirdest laws that most places follow imo