Oh this is easy. Because their are so many obstacles involved in gettin the sound from your speakers to your ears. If you have only two speakers screwing it up rather than 5, 7 or even the dreadful 10 the outcome is alot less noticable to your audible perception than multichannel. there is to much going on in regards to phase, power consumption needs and room acoustics for a multichannel system. No one pays attention to acoustics in two channel system never mind a multichannel set-up. Of course this is just a general statement. There those that have paid great attention to wonderful multichannel setup. And to those i tip my hat. But, by-inlarge multichannel will always sound a lot less involving and way to destracting than most two channel systems.