Why don't modern planes and ATC centers have good-quality audio for communication? For example in this video:
Or basically any other example of pilot communication(some are worse, some are better).
This is not terribly bad of course, but this is comparable to a cheap $4 headset, the sound is so distorted. This can cause trouble when a pilot does not understand some words and asks to repeat the sentence. And even more problems if the pilot or flight dispatcher are not native English speakers.
Is there some technical reason behind this, like antenna/signal limitations within the plane? The quality is the same when the pilot is just taxiing on the ground, so I suppose this has nothing to do with speed or altitude.
P.S. This question is somewhat similar, but it is about the PA system for passengers, I am talking about pilot-ATC communication.
Though I accepted(honestly - by peer pressure) answer from TomMcW, who gave quite good technical details on this subject, I personally like the answer by Anthony X, who pointed out very important fact that the systems should be changed everywhere worldwide in a very short time period and that is what probably the reason no major changes were made during last couple of decades. So I suggest to read his answer too, not only top-voted one.