I think this is in part projection of insecurity by low/middle classes, because rec sports are definitely a social status signal for upper classes. It's also "socially acceptable" to waste hours of time watching TV instead of hustling. Another data point as a counter is the popularity of video games. The only people saying they should just be for kids are aging boomers (in general)

I do agree though that there is a stronger social pressure to be enterprising. For young Americans I think the obsession is social media or youtube