Sure, but just look at the revenue. Some do build it out (and I'm sure HN has higher percentages of "home theater types" than most) - but the average house? It's a TV.
Thinking over everyone I know who has a TV, I'm the only one with a receiver connected. I think one has a soundbar.
A lot of it is that the design of good home theater equipment is ugly and not spouse-approved. My wife simply will not tolerate big black speaker boxes and a black stack of receiver equipment in the family room. No matter how well it’s hidden away. And I know a lot of families that have the same desire for a nice looking living space.
Personally I think that the "takeover" of the living room by TVs and home theater has been one of the biggest "mistakes" in modern home design - they should be relegated to the basement or some other locale.
This is actually what I did in our previous home. Installed round Monoprice brand in-wall speakers, and hid the AV equipment in the next room, one wall away. It sounded--not too bad.
