I think it's a case of both drivers and kids having a bit of common sense.
Ultimately, in my opinion it depends on the street - I grew up on a quiet cul-de-sac with a lot of kids which was probably more play area than thoroughfare, and so any driver with half a brain will expect the possibility of there being a game of football around the corner.
Equally, the A419 is for getting from A to B (motorised or not), not kickflips and roller hockey.
Obviously these are two extremes - where exactly the line is, I dunno.