I'm not, and never have been, a dub - but I was brought up in a fundie sect/denomination (PB) and they had the same problem.
One of the things that worries sects most (IME) is the 'danger' (as they perceive it) that there are not enough potential mates (or partners, call it what you will) within the sect ('Organisation' I suppose in JW speak) and youngsters/teens/young adults will follow their hormones out of the religion. IME when I was a post-pubescent male teenager a pretty girl with the promise or possibility of carnal knowledge to whatever extent won out over theology or the fear of eternal damnation any day. And I wasn't alone - I remember one young lady telling me that her greatest fear was being 'sent back unopened'. I don't think that those basic feelings have changed much.
It has been said many times but I think it's worth repeating. The greatest influence that pulls people (not just teens) away from WTBTS and other controlling cults is access to the internet, social media, FB, Twitter, etc. One doesn't even need a computer now - a (free) mobile phone on a £15/month contract gives all the access needed.
I suspect that it won't be long before the only 'JW Youths' (isn't 'youths' such a clumsy and pejorative term?!) still 'in' will be the socially or otherwise challenged.
No offence intended.