I'd definitely say it is in decline, especially for males under 25, and to a lesser extent, males under 35. I have plenty of friends and have worked a lot of jobs over the years. Not one of my co-workers over the last 5 years of working had anything beyond a cheap HTiB. I'm the ONLY person in my immediate and extended family that has anything I'd call a decent setup. Parents have a 5.1 HTiB and everyone else uses TV speakers. The first words that usually come out of folks mouths when they see the crap I have is, " Holy crap!! "
Back in the 1980's almost EVERYONE I knew had some sort of audio setup with a pair of 3-way dinosaur speakers with a 12" or 15" driver. Seems that kids these days are perfectly content with heavily compressed audio and video played on a very small screen using Bluetooth speakers.
Denon AVR X7200WA, Emotiva XPR-5, Emotiva XPA-7, Sony XBR 75" 850C, Oppo BDP-103D, Roku 4.
DefTech BP7000SC (L/R), CLR3000 (C), SM55 (FH), UIW BPZ/A (SB), UIW 75 (TM).
JBL L7 (Sur), EoSone RSR 350 (RH).
PC 2.1 setup. Emotiva Stealth 6, SVS SB2000 sub, Emotiva DC-1 DAC.