That's actually close to another very important point. Most movies come with a 5.1 mix nowadays, and people watch them on a stereo system. Most players use a very simple formula when converting 5.1 to stereo, something like say Lout = 1/2 Lin + 1/3 SLin, Rout = 1/2 Rin + 1/3 SRin, and leave out the center channel completely. This is also done inside of TVs etc. The center channel gets dropped completely! And sometimes dialogue is only in the center channel - not all of it, but there are some lines every now and then that just only ever come out of the center channel. Those are lost.