Not sure I understand why. We had our fun with it, why should I care if people are still playing it 20 years from now? We're not curing cancer here, we're killing time and in the end, blowing a bunch of money on ourselves. It's not like it's some noble undertaking that your son should feel obligated to carry on.
This thread highlights the positive impact of the hobby - getting to know people, from across the planet, and making lasting friendships while learning a little about history and sharing passions for that history. That's all good stuff. But ASL is just the vehicle for that - an old, clunky, expensive vehicle. When you buy your son his first car, will he get a rusted out 1977 pickup truck, or does your son deserve something with decent gas mileage, air bags, crumple zone, heated seats, and collision detection?