^Pretty much the same thing happened with Rock & Roll back in the 50's and 60's. It may be hard to appreciate now, but back then the music of Chuck Berry, Buddy Holly, Little Richard, The Everly Brother, Jerry Lee Lewis etc. etc. was for the most part considered to be music solely for young people. The expectation being that when the kids got older they'd leave that behind and start listening to grown up music just like mum and dad.
However, just like with video games, it came as a bit of a shock when the next decade rolled around and the kids of the 50's became the adults of the 60's and didn't grow out of Rock and Roll but kept with it and the new generation of musicians that grew up with it, evolved the medium further into a much more mature art form.
Video games are pretty much in the same place right now. Of course this brings with it the terrifying prospect that we have the video game equivalent of the disco era to look forward to, if indeed it's not already upon us. Either way, I'll be giving that a miss.