I agree that we have measuring equipment to measure every aspect of sound that is audible to human ears. However, it is much harder to measure subjective preference or the emotional enjoyment that music brings to individuals. It is possible to do a large sample size observational study for preference or perhaps measure the blood flow to the nucleus accumbens and dopamine blood levels per individuals to kind of objectively test for that, but seems pointless as the easiest way is to simply ask the person what they think.
A key component that people forget when focusing on measurements is that not all measurements are done equally well. There will be inherent discrepancies in measurements from different sources due to different set-ups and measurement techniques. I approve of more objective data correlating to headphone performance, but I find it hilarious when random modders post their home-made graph showing the slightest difference between another graph and claim xyz.
Was that difference beyond the scope of measuring variability or manufacturer variations between drivers or even random chance? Was that value statistically significant? Is that difference in value within the threshold of human hearing being even able to detect?
There are a lot of unanswered questions in this hobby and a lot of pseudo-science passed off as objective information without proper statistical analysis. There isn't even an universal controlled measuring standard or procedure for audio components. It is no wonder a lot of people view this hobby to be a bit sketchy at times.
Yes, there are people that just buy what they like, but for some of us looking for sonic improvements that can be quantified, there is a dearth of information within this hobby. imo.