The demise of quad appears to be an example of "great product and what an improvement -- but no one cares".
It probably wasn't the first -- FM had been around for 30-40 years in different forms before people caught on. Other new tech didn't take so well -- AM stereo, SACD (the only ones that sold were probably the dual format CDs), DAT (only used in studios), Minidisc, etc. You might be able to add HD Radio to that mix, although I think it may have a future, as some HD2 channels get ratings, something that wasn't happening a few years ago.
I never knew anyone who had a quad receiver, quad stereo, quad anything. I recall seeing a few of the quad LPs. Deep Purple, when they remastered Machine Head, included a quad mix of a couple of the songs (Maybe I'm A Leo and Lazy) because they sounded different in stereo.