There are some very good points brought up here. However I think we are overlooking a basic change in youth behavior that has occurred nearly world-wide over the last ~20 years. That is the tendency of young people to A. avoid risky activities outside the relative safety of "experiences" such as amusement park rides and other programmed events, and B. a decreased tendency to initiate an activity such as building or repairing things. I am sure all of you have witnessed both these characteristics in today's youths. The reasons for this are many and may include "helicopter parenting", child coddling and easy availability of simulated electronic experiences.
Now add to that the reduced amount of income experienced by many youth as "good" jobs get harder to obtain. Soaring is expensive. Hang gliding and paragliding are far less expensive. Hence the huge difference in numbers (see Swiss post above) of the remaining youth who still have the "adventure" gene active within them.
In short, there is little we can do to attract youth into sailplane flying in any large numbers. As someone pointed out, that is probably just as well as there are not enough resources to handle such an influx anyway. The best we can manage is to introduce youth to it and hope they return later in life when they can afford it.