I remember that when I was in grades 3-5, probably 95% of the boys my age (including me) participated in the Cub Scouts. But that percentage was, I think, unusually high because most of us were "military brats" whose fathers (or in a few cases, mothers) were stationed at a small US base in Turkey. So being a Scout was "practically mandatory" (though, of course, not literally mandatory) because of the military culture that prevailed on the base.

But in public schools back in the States, the rate of participation in Scouting programs was generally lower -- unless you happened to belong to a religious community (such as the Mormons) that strongly pushed kids to be Scouts.