NAO
you said it, you only bloody said it!!!!
"in our day...."
Too much sedentary entertainment (tv, video games etc).
Children tend not to "play out" as often - not enough open space to, not considered 'safe' to allow children out without supervision any more.
Most parents have cars now - car to shops, car to school, car to wherever.....
I remember walking everywhere. Twas common two walk a mile and a half to the local high street to wander up and down visiting butcher, grocer etc, and then the mile and a half back - from age 3 to 4 upwards.
Not as much sport or PE at school. We'd have PE one day. Netball/football another. Country dancing (dear god that was bizarre), rounders another day, or gym if it was raining. (Drops even more at secondary but that's not the issue here....).
Have to say, the school my DD has started at (today, as it happens), has a programme in place whereby they have at least 10 mins a day of some 'activity'....will see if i can find info on it........