While all valid points - The truth is the boy scouts have declined for 2 very simple reasons.
1- Increase in Org sports (Including Travel teams)
2- Video games.
Girl scouts are dropping as well.
As youth sports participation has increased, and esp the Travel sports (Which become year round) any kid who is a bit athletic tends to participate more in that.
Meanwhile kids that arent in that group found video games and would rather play that.
yes -Then there is a group that arent either -And they continued with BS / GS - but that number has declined.