I'm both an audiophile and an amateur musician. I've studied harmony and counterpoint and I do a little piano improvisation in classical styles. I only have a digital piano at home, so when I'm improvising, I'm focusing on the notes and chords and a rough sense of the rhythm.
If I listen to a recording of Glenn Gould performing the C# minor fugue from the Well Tempered Clavier Book 1, even on an iPod with earbuds I can tell the notes he's playing and his rubato, so I can enjoy it to some extent.
What does my main headphone system give me? All the qualities beyond notes and rhythms! For example, beauty of timbre. And especially microdynamics. In classical performance by the best players, there's a sophisticated use of small dynamic changes. So much more of the performance comes through in a system with dynamic resolution. It's worth sitting for a while and doing nothing but listening.
Why do musicians care less about home audio quality? I think it's because they are so connected in body and mind to musical patterns that they can sense them and feel moved by them even in poor reproduction.
They invest their money in their instrument.
I've noticed when driving home from an L.A. Philharmonic concert, listening to classical KUSC on the poor quality car system, I am transported back to the beautiful sound I just heard in the concert. If I hear horns on the radio, I think of how beautiful and powerful the live horn sound is. I used to be a brass player, so this is easier for me than if I had had no exposure to live sound. Now just imagine being exposure to live orchestral sound every day. I'm sure that simple systems will sound very evocative to you.
