I spent about 3 years after university being what some here would probably call a useless layabout. I was on benefits most of the time. I did a lot - environmental and peace activism, local politics and community stuff, music, and all that and I did some occasional paid work, mainly for charities - but made no real effort to get a 'proper job' or pay off my student loans. But in the long term it did me, and society in general, no harm at all. The one thing I didn't do was live with my parents, but since they sent me to boarding school at the age of 8 it wasn't as if that felt like an option...
I think what I'm saying is don't worry too much about the 'idleness of youth'. People work out what they want to do in life at different stages. Those who seem driven and successful early on often burn out and change direction radically later on. People who seem to others to do nothing in their early 20s can find a path later. Of course there are some people who are permanently lazy and don't care about anything, but there's really not a lot you can do to change them.
