In the rush to all things digital, you see the limits of the technology in areas like that. If you skip HD and move back to some old 480 line display you might see the old smooth images. But if the content is digitized, you will see pixelation in high motion areas.

Why this is not considered an issue is, well, because to cure it we would need about 10 times the digital data and most stuff looks fine. Maybe this is the old quantity over quality again issue.