It's a great question actually. I've wondered about this myself some lately.
A friend and I were comparing listening sessions recently and I realized we like to listen at different volume levels. And, thoughts around how each of our systems will sound different if he's listening at 80db and I'm listening at 70db most of the time.
My system's character changes overall when comparing 65,70,75,80-85db listening levels. I don't care for how my current system sounds when the volume level is turned up really loud. My level of interest and engagement drops notably.