Hmm, I've never really noticed this, but now I can't unsee it. Tom Scott explains in a very clear way why moving bits in video can sometimes degrade YouTube video quality. It has to do with how much information is compressed in a streaming video and how that information is channeled to users' computers across the internet. More moving parts in a video mean more data. But with a bottleneck of speed, that video can sure start to look crappy.