Reduce impact of crowd crushes, evac lane for medical emergencies, logistics of distributing supplies/food/fliers, possible regulatory restrictions, it just looks nicer, easier to organize and disperse from, etc.

Basically all kinds of reasons that a collectivist society would want to, it can be a pretty stark contrast for Americans who (again, generally) have a culture to go out of their day using extra effort to deliberately make others lives worse.

Although Korean culture is equally as rotten to the core in other ways, there are still signs of their glory days like this