The same old story,
"save money", (which is Arabic for "increase profit") by degrading quality knowing that the consumer does not have a competitor he can turn to for a better product. I've noticed the pixellation, too, but I always thought that was a totally different problem caused by legitimate transmission or satellite issues. It's reassuring to know the problem can be traced to the same source.
It's also reassuring to know I'm not just seeing things, my wife has often screamed in frustration at the pixellation (plus loss of audio, frozen frames, and complete interruption of signal) but she has never noticed the compression anomalies you describe. Thanks for the response, I have just won a domestic wager.