There have simply been a huge number of people who have begun streaming at a modest level and subsequently moved upward in sound quality and performance. They are not delusional or gullible.
51% of Americans believe in UFOs, even though a vehicle traveling at the fastest known speed of any non-gas, non-particle object in the universe (2.3 million MPH) would have to travel 12,000 years to reach us from our nearest star (and theoretically wormholes, if they exist at all, are impossible for travel). And 40% of people believe in ghosts. I have no doubt people "think" they hear a difference. The mind is a powerful convincer. But there is no objective reason that they would hear a difference. Both the human ear and frequencies are measurable, and have been for decades, and the measurements say any differences in equipment continually show that those measurements are beyond the level of human hearing. And having worked on software and networks for decades, I know how the internals of these devices work and what the variables can be. Can the sound of a DAC be different. Sure. If you want to see how read the book Schiit Happened. They tweaked the software of the analog conversion by ear. I wouldn't doubt if other companies do/did that as well. But that's not an accurate conversion. And those tweaks show up in measurements. Accurate conversions are always formulaic.
The belief in something despite overwhelming evidence is the definition of belief perseverance that I mentioned in my previous post, so I'm not attempting to change anyone's mind. That is likely impossible. And some people actually prefer inaccurate sound, hence the continued existence of tube amplifiers. I have nothing against that. If you prefer a particular inaccuracy that cost an extra $10,000 and you have it to spend, more power to you. As long as it's not hurting anyone else. But for those whose goal is accurate reproduction and preservation of their capital, myths and subjective perceptions are antithetical to those goals and I'm just pointing out alternate options and their reasoning as I always prefer others to do when I'm researching a subject. Humans are infinitely fallible, and "because I heard it" without an objective context is not a compelling reason for someone to start throwing their hard-earned money around anymore than "I saw a ghost" is to start buying EMF gauges and thermal cameras. The first question to answer is "why?" The "why" is answered by the measurements or psychology. Either can be just as powerful based upon the individual. Measurements usually produce cheaper results.