Do you know the story about the farmer who said "I'm not greedy for land; I just want what joins mine."? Even though carrying such a practice to its logical extreme could wind-up with the farmer eventually owning the entire planet or - given space travel - the entire universe, I can still understand how that farmer might actually believe that what he was saying was reasonable. After all, audiophiles say the same sort of thing all the time.
When audiophiles say it, though, they put it a little differently: "No," they'll tell everyone, especially themselves, "I am NOT trying for sonic perfection - I know that that's impossible -- it's just that my system has this (Let's call it "Thing L") that's really annoying me"
The problem is that every system and every one of the components that make it up has an entire alphabet of sonic characteristics ("Thing A" through "Thing Z") that can eventually drive you nuts and that can eventually need to be fixed or gotten rid of.
It works sort of like this: My system, which I love and was completely satisfied with when I first bought it, is starting to lose a little of its luster... After a whole lot of serious listening to a whole lot of different program material, I've figured out what's bothering me: There's something wrong with the "Thing L", but now that I know that's what it is, I can just ignore it... Now that I know that there's a "Thing L" problem, I CAN'T ignore it... No matter what I play, that's the only thing I find myself listening to...
Eventually, something about the system that was, at first, not even noticeable becomes an obsession and something has to be done about it. But how can that be? If it's such a problem now, how could we not have noticed it before?
It all has to do with how people listen. Instead of taking in all that's there, people really just hear whatever it is about the music or the sound that "turns them on"; and we all get turned-on by different things. Women, for example, tend to listen to the words of songs, and to care less about either the music or the sound. That's why, unlike us, they always seem to know the words to every song, and why there are so few female audiophiles. Men, on the other hand, tend to pay less attention to the words and more to the music and the sound, and the results are obvious.
Even among men, though - even men who might reasonably be expected to have a "trained" ear - different people listen for different things: For me, it's imaging and soundstaging. For one manufacturer I know, it's the attack and decay of transients. For another it's "harmonic richness". One friend of mine who's a reviewer for a major magazine listens for "believability"; another likes his sound "quick" and bright and another likes it "slow", and chocolate-brown. Outside the industry, it's just the same: For some people, the bass is the thing to listen for; for others it's the treble; or "clarity", or "dynamics" or "freedom from distortion". I've even met people who don't care much at all about what the music sounds like, as long as it's head-crushingly LOUD.
All of these different characteristics - loud, bright, clear, dynamic, and so on - are the "letters" of that sonic alphabet I mentioned earlier. Every system and every component has them all in varying degree and, because we each give them different priority, it's like we're all reading different books; all written in the same language, with the same alphabet, but with the letters arranged differently. That may be why "double blind" testing of cables or equipment so often fails; perhaps the testers don't agree simply because they're all listening for different things.
To us as audiophiles, an even more important thing may be that, even though when we first listen to something we will hear whatever is most important to us; as we listen more and become more familiar with a system or a component or even a particular recording, we start to hear more of those "letters" that we missed the first few times around. That's why we don't hear that annoying "Thing L" when we first buy the system, but notice it and come to find it increasingly unbearable as time goes on.
It's also one of the prime reasons why we keep having the same experience over and over again: Imagine that, having nailed-down what's annoying us, we discover, by long hours of critical listening and repeated substitution of both components and program material, that its source is our preamp. Aha! We cry, and take off for our dealer or the internet or the reviews or the wisdom of our audiophile friends to find a preamp that has great "Thing L". Let's suppose that we find one, and buy it, and take it home, and put it into our system, and listen to all of our favorite or most revealing records or CDs and we LOVE it and we let out a long sigh of satisfaction and settle down to a day or a month or a year or even more of loving our system again, until, at some time later, we discover that... there's a little problem with "Thing J".
Isn't that exactly like the farmer with the perpetual desire for more land? We're not after perfection. We know that that's impossible. All we really want to do is to solve this one little problem...