In my opinion, it really isn't sound quality that is the number one driver for people purchasing an integrated amp. most people are not audiophiles and don't sit and listen to music for hours on end. They have "lives" (notice the quotes?) and listen to music while doing other things. So, music is background music to them. don't get me wrong, they appreciate good sound, but I believe in most cases (not super high end), aesthetics, space, costs, less complexity are the driving issues in the purchase.
Most places (Europe and other countries) simply don't have large living spaces that can be taken up by lots of equipment and cabling.
People that are forced to downsize also want less complex equipment and have less space and time to tinker.
Consider, that many people simply have no clue as to the costs of high end equipment and are quite taken aback when they walk into a high end store and see what's offered and the prices. That's like being prepared to purchase a subaru and mistakenly walking into a Mercedes dealership. Opp, my bad, time to back out quietly.
I love music, played many instruments and can't stand it when music doesn't sound real or right. So, I made a conscience choice to make music and listening a priority in my life. I can't tell you how many people I know think I'm absolutely nuts.
But, they have no problem with distinguishing high end cars, watches, etc. interesting.
Also, the Wife Acceptance Factor (WAF) is still very much alive and well. I am starting to see separates looking quite nice, but, this is still a sore spot for many. Most integrated amps look nice.
I don't see a new fascination. Integrated amps or receivers have been around for as long as I can remember.
When I'm ready to downsize, I would be very interested in a very nice integrated. I'm not sure I want to be worried about tube amps later on. I already watched on of my Audio Research REF 250 amps go up in flames when a tube failed. it took out resistors and capacitors and traces. I was watching when it happened. $3,000 in repairs later it is perfect. And those were brand new tubes purchased from a tube supplier that claimed they were matched tubes for that amp. Never again. I will only purchase tubes from Audio Research. they will pay for repairs to their equipment if tubes they supply fail. lesson learned. However, a very good solid state amp or integrated amp that can drive my speakers (which may also change when I downsize) is the next step in this adventure.
enjoy