I think a big part of that is that young people are not into "collecting". My nieces and nephews tend to be more minimalist. My wife's parents passed away last year and the grand children had very little interest in taking home any of the china, furniture or art work, or any of the many trinkets that older people like to display. Some of that comes down to taste, but there is history behind the art work and other items like coin or stamp collections but those things don't seem to hold a lot of meaning until people get older.
I think I got my daughter started on audio by getting her progressively better headphones. Once you get used to listening to a good set of Sennheisers it's hard to go back to stock earbuds. As a poor student, she cobbled together various components, often from friends who gave her some old equipment, but she ended up with a decent receiver and turntable. Once I replaced her no name speakers with the KEFs that I restored, it sounded pretty darn good and her partner uses the system more now as well. It will be interesting to see whether they consider a home theatre setup when they get their first house.
My son spends most of his time on his computer so he uses ear buds a lot. I've been upgrading those on occasion but he simply isn't one to play music over speakers yet. He can hear my system through the air vents when I crank it up though.