Scotty, thanks for the reminder and the link.
Lots of reasons for the relative loss of interest in audio...
50 years ago (plus or minus) hi-fi was about the only high tech game in town (TV being too crude to be said to have fidelity). So we've lost that crowd but picked up the vintage crowd. I suppose there's a vintage TV crowd, but hopefully not to watch 12 channels of fuzzy B & W.
We also lose many in their formative years to video games. It has been said that the those under 25 or 30 in 1st world countries consider virtual reality as more "real" (relevent/important to them) than the physical universe (the "Matrix" dread is here).
As a culture we've become addicted to stimulation. More the better, anyway you can get it. Even nursing homes have TV and separate music both on at once in the same room. We can't seem to drive, read, shower, toilet, cook, be put on hold, entertain, or eat without music or TV.
We lost many in the rush to convenience at any cost (oven versus microwave cooking; sit-down restaraunts versus drive/walk through; hand written letters with a dash of the author's smell/perfume versus e-mail, text messaging, talking in person versus voicemail; going to a live performance versus listening to a recording). That's where car radio/Sirius, cassette, and MP3 come in. Some would argue that CD and computer music servers don't provide the fidelity of vinyl.
Certainly CD or computer music servers take from the physical interaction and "hobbiest" aspects of vinyl or open reel formats.
OTOH we listen to more music than ever before, its just nearly all recorded.
The points I would consider debatable is what a minimum level of high-fidelity is and if the level of fidelity has increased on the whole or not over the years. Development of a reasonably affluent middle class has allowed for a wide population to have access to what I'd call hi-fidelity. Advancements in technology has also aided in this access. Keep in mind that it was just announced that gas prices have reached inflationary parity from 1980. So the modern equivalent to my $500 Hafler pre/power amp kits that I bought in 1980 should cost $2500 today (and that pre-amp was "lightly" built).