Chris, this issue is addressed directly in the latest
Sound & Vision magazine -- in a column as well as a feature story.
You have to bear in mind that hobbyist audio always has been a fringe pursuit. On the other hand, home theater has been a mass-market phenomenon ever since DVD arrived on the scene. Most people are more impressed by pristine video, apparently.
A case in point: my first wife. When we were living together, my continually evolving high-end audio system -- easily better than any other kid's on the block -- could not have underwhelmed her more. She just didn't get it. (A divorce, then, should have seemed inevitable.

)
Similarly, how many of your friends, coworkers, and relatives have ever put in a lot of effort assembling music systems during the heyday of two-channel? I bet you were the only one among them, eh?
Yet, seemingly, everybody loves a pretty and colorful picture. DVD has blown them away -- and the 5.1-channel surround sound is but part of the equation.
It's just the way things are. Not good, but that's reality.