Why did home theater buyers readily accept surround sound, but consistently reject multichannel music formats? From Thomas Edison's very first phonograph in 1877 through the late 1950s, monophonic sound was the only way people heard music at home.
Stereo arrived in the late 1950s on LP and analog reel-to-reel tape, and stereo has remained the most popular music format to this day. Quadraphonic (four-channel surround) debuted in the early 1970s, but didn't survive the end of the decade. People didn't want to plant four speakers in their living rooms, and the Quadraphonic Wars ensured the format's early demise. I remember massive confusion over the distinctions between CBS' SQ, Sansui's QS, and JVC's CD-4 LP quadraphonic formats; along with the various quad analog tape formats.
You would have thought that when the SACD and DVD-A multichannel audio formats debuted in the late 1990s they would have been embraced by the existing home theater market base. They already had all the speakers and a subwoofer, but the home theater crowd was uninterested in the two competing multichannel music formats. Besides, the folks who wanted to listen to music in surround were already doing so. Without investing a penny in an SACD or DVD-A player they could play all of their CDs with Dolby Pro Logic surround processing, and enjoy 5.1 surround from stereo CDs. That's still true today.
Two high-end speakers can create such a fully dimensional soundfield that few audiophiles were tempted to expand their hi-fis to 5.1-channel systems. In the early 2000s I reviewed lots of SACD and DVD-A players and discs, but as soon as that work dried up I happily returned to two-channel music.
Obviously, 5.1 surround makes sense for movies and home theater, mostly because 5.1 was a logical outgrowth of movie theater surround systems. Movies, after all, have had surround sound since the 1950s. Movies and surround go together like popcorn and Coke.
Stereo doesn't even have a formidable music-surround format gearing up to challenge its long reign. Now that most people listen to music over headphones, a new surround music format would be an even tougher sell.