It's still fun, you just don't have the time anymore (I feel really bad if I take out a 3-hour chunk of time to play a game, or a real-time game which demands 1-hour of continuous focus).

Much as I don't play football anymore but still watch it, I also follow some games :) and so do many friends in their late 30s / 40s with families (mostly the same ones as others in the thread, like Magic: The Gathering, League of Legends, Hearthstone, etc.).

They grow out of playing video games perhaps, but there's a whole world of content for folks who still like video games but don't play them as much anymore.