Anecdotally my experience is dramatically different.

Last week I arrived by car right near the beginning of dropoff time. Pulling in right in front of me was the mom of one of my kid's classmates, carpooling with another kid who lives in the same apartment complex. The three of them met up as soon as they got out of the car, and then another one of their friends (who lives across the street from the school and usually walks) joined them from his driveway. They met up with a 5th friend before they crossed the street.

Then I walked - well, more like ran - with the 5 of them down the 111 steps that take us from the street level to the schoolyard. When they reached the bottom, they met up with 3 more friends who had just been let out of the drop-off zone in front of the school itself. Said a quick goodbye to my kid, but he wasn't really paying attention, he was already ensconced in his pack of 8.

I've gotten there with my kid before drop-off time, walked down the stairs with him, and there's been a pack of about 20-30 kids and 2-3 parents usually milling around before the school gates open.

I realize that this is somewhat atypical in 21st-century America, and we specifically chose this community because, well, it actually has a sense of community, but it's not unique. In preschool I'd take my son over to his preschool bestie's house (she lived about 2 cities away), and there'd be a whole pack of kids roaming the neighborhood going over unannounced to each other's houses.