@larryi +1
As my system has gotten better, less and less volume is required. I am sure there is more than a couple reasons. But the first most obvious is the noise floor. Less expensive and old systems like in my youth had very high noise floors. Often it takes experience to “hear” this…. It is the jacked up quality to the sound and pressure on your ear drums. So, turning up the volume you are looking to increase the dynamics… the contrast. This also increases the noise floor.
Good systems tend to have a place where they sound best, balancing noise and dynamics. Great systems sound great at all volumes. This I one of the marks of a great system. They are engaging at a whisper and 90db.
I remember being impressed going to a high end audio store in 1980 and achieving 110 db. The salesmen and I were really psyched at what we had done… but my ears were practically ringing. It was the incredible volume of the stuff in between the notes.
There are other reasons, faster bass transients…. And greater articulation.
Decade after decade as my systems improved the volume required the music sound great and dynamic has come down. While I used to play in the 90db range in the 1980s… now in the low 60’s to 70’s db. The music is completely satisfying.