Enjoyed your post, Leedistad, but I don't agree with your point about asking this question being akin to asking why more people aren't into model trains. Playing back / listening to music is an almost universal experience, and the fact that such a vast percentage of the people who experience this never move beyond the cheap stereo / boombox / iPod playback approach is a bit bewildering to me.
I think this post has lived so long because you can look at the question so many different ways, but one version, and the one I'm using, is to question why, when almost every other pursuit (you mention several) has luxury versions that people pursue. So, I'm not wondering why more people don't pursue $10K preamps and the like, but a $1K-2K system built around Creek gear, or the Arcam Solo, or any of a number of other nice, lower-cost manufacturers, should have more market penetration than it does.
To put it another way, off the top of my head, I could name several acquaintances who are "into" wine, several who are into bikes, motorcycles, power boats, some who are into art, some who are into watches, many many who have invested in expensive video, and probably even a couple who are into model trains. But I almost fall off my chair when I come across somebody who has invested past the bare minimum on audio playback.
As you say, different strokes, but I still find it odd that so many people listen to music, but the acquisition of decent playback gear is just absent from most peoples' world.