I've been thinking about this a lot since the thread started. I've had some long-winded responses in mind, but I think I can distill it down to the following.
1) For whatever nature and/or nurture reasons, my brain is wired to respond to music in an intensely positive way.
2) Listening to music also evokes a strong desire not only to listen to it but also to create it myself.
3) HOWEVER, I do not enjoy the music itself as much when I am playing alone than when I am listening to it. I shift from audience mode to performer mode, which is mentally very different for me, and not as positive.
4) HOWEVER, when I perform for others, those two seem to collapse together in a good way, and I enjoy the music even more than simply listening to it. For whatever personal psychological reasons, the presence of an audience allows me to inhabit the audience mode even while in performer mode, and then some.
That's about it.
Enthusiastic but mediocre amateur.