It seems some who don't care about, or have abandoned any semblance to the real thing can't grok why anyone else would care.
Here's my approach:
The reason I got in to high end audio was having some life-changing encounters with audio systems, where the music sounded more "real" than I ever imagined it could (e.g. when a pal bought Quad ESL 63s and I came over for a listen, I was just shocked at the sensation of an acoustic guitar, a violin etc just sounding like it was performing RIGHT THERE, not even seeming to come from speakers, and with a measure of realistic timbre and detail that astounded me. My first real audiophile purchase became the Quad ESL 63s (and later added subwoofers).
So one of the things that attracted me to high end audio in the first place was a semblance of accuracy and realism, in particularly timbre. I can enjoy music on anything - my car stereo, our smart speaker in the kitchen, I even love it coming from my iphone speaker! But what I get from my 2 channel system is not only just the musical content, but I get more: I get the sensuousness of the sound itself. I get *some* of the dynamics and timbral character that I find so involving in live instruments. If someone is playing an acoustic guitar (or if I'm playing mine) I can just sit there and drink it in, not only for the music, but for the sensuousness and richness of the harmonics, dynamics, the sound "quality." Any system that gives me at least some of that is one that I simply enjoy more.
As for believability, like most I'm quite aware my system will never sound just like the real thing. And I also listen to lots of music that isn't even made from acoustic instruments. But I do find that if my system captures certain aspects that I like in real sound sources, it's more satisfying AND it helps me sink in to the "illusion of live" more easily, when I want that. So for instance, my system will never reproduce the acoustic presence, dynamics and power of real drums. But so long as it recreates certain elements that I love about real drums - e.g. when drum snares have that recognizable papery organic "snap" rather than sounding like some thick burst of white noise -that is both "more right sounding" and more satisfying. It also lets me sink in to the illusion of hearing through the speakers to a performance, when I'm in that mindset. Plus, I find when a system sounds timbrally and dynamics more towards the "real thing" with acoustic sounds, it is also more satisfying with ALL the music I listen to, including electronic music.
But back to the realism thing, in those instances where I indulge more in the illusion, to me it's an attitude similar to watching a movie in a movie theater (or on my projection screen). The movie is never going to recreate reality - the image is flat, it doesn't have full color and contrast and detail like the real thing, there's all sorts of artifice in film making, just as there is in music made in studios. But the reason many movies (at least those striving for believability) take some pains to get SOME things more like real life - e.g. the script, the acting, the set design - is because when you get certain elements more like the real thing, it helps the viewer sink in to the illusion of reality created by the film. The viewer is willing to do his part in suspension of belief, and it's helped by some verisimilitude on the part of the film makers (and on the quality of the viewer's own home theater system should that be the case).
Same with my approach to a system that gets some aspects routinely "more like the real thing."
I was listening to a symphonic recording of the Star Wars The Empire Strikes Back.
It was simply startling in how vivid and powerful it sounded. Now, the last thing one might expect an average system to reproduce realistically would be an orchestra.
But my systems reproduced the timbre of strings, woodwinds and horns very much as I think they sound in real life. And even if my memory is wrong, or imperfect, it's only MY perception and memory that I have to fool. So with eyes closed, I just had to make a little mental adjustment for scale. The spread of the symphony created by my Thiel speakers was quite large, but certainly smaller than if I were sitting right in front of a real symphony. But if I just made a little mental adjustment, and envisioned I was sitting at the back of the hall or from the balcony, suddenly the scale of the symphony clicked in to "believable" and frankly it was amazing how easy it was to get the illusion of sitting in a hall listening to a real symphony. And that only added to the thrill of the music itself.
So...I certainly get the attitude "I don't bother looking for realism, it's an impossible goal and I just want to hear whatever the recording sounds like and I'm happy."
But those of us who still use real life sound as a sort of north star or barometer haven't plunged ourselves in to perpetual dissatisfaction or are doing so in some unrealistic goal. Approached sensibly with realistic expectations, our systems can be deeply satisfying, having been somewhat guided by what we like in real life sounds.
