Because they're producing for surround sound systems you can't be bothered to deploy or operate optimally. 5.1, 7.1, etc. The "center" channel, in particular,

Because they're producing for surround sound systems you can't be bothered to deploy or operate optimally. 5.1, 7.1, etc. The "center" channel, in particular, is where the bulk of dialog is rendered and if your system can't synthesize that channel extremely well on the loud speakers you have then dialog suffers. Also, if you lack a surround sound system -- say you're using a pair of stereo speakers -- all the audio is mixed to these few loud speakers and the spatial segregation that we two-eared beings use to isolate sound is lost. There is no fix for that; the work was produced with the assumption of surround sound and driving all of that audio through a pair of closely spaced flat screen speakers/sound bar/whatever screws everything up spatially and dynamic range wise. The audio is tailored for the minority of people that invest in "home theater" while most people, even those that can afford to, don't care enough about teevee to build such a system. In theory one should expect media to support non-optimal cases, and provision for exactly that exists, but this costs more production money to do correctly and so it gets neglected in various ways. Obviously they don't neglect the demanding consumer with his costly home theater setup because they'll get pilloried, so they half ass the other side.