I think this is it. Cars. The Fitbit general population statistics - which I would presume is a self-selected group of at least activity interested people, are

I think this is it. Cars. The Fitbit general population statistics - which I would presume is a self-selected group of at least activity interested people, are quite scary in terms of the large number of people in the <5,000 steps bracket, and the relatively few in the > 10,000 bracket. 10,000+ steps is a normal day walking around London for me, to from work etc. but if I'm driving I may not even get up to 3,000.