Do you think the younger crowd are that into forums in the first place? AFAIK they get their fix on facebook and twitter.
There may be a certain amount of truth to that, but it doesn't seem to be a problem for many other forums I use. This place used to attract plenty of younger posters in the past but without a doubt the tone has changed over the years. Posters have been increasingly permitted to be more hostile and condescending towards them, I can understand why they'd be put off.