I have been thinking about this more than can be healthy recently.

In my kids school there is an open yard, through an open gateway, into another open yard in front of the school

         ┌─────────┐
         │         │
         │         │
         │         │
         │         │
         │         │
  ┌──────┴───xx────┴──────────┐
  │                           │
  │                           │
  │                           │
  │                           │
  │                           │
  └───────────────────────────┘

Lets say xx is the gateway. At pick-up time this is where parents will stop to talk.

This used to drive me mad as it was literally a bottleneck and i wondered why people could be so inconsiderate, but I started to observe, and people would meet, greet each other, and then walk together to that point to stop and talk - and everyone would do it, it is like they are drawn to that gateway to talk - and it has baffled me, i really think we are hardwired to do it, despite the impracticality of it for other people - why??