From my comment
All you subscribers who think you’re getting over 100 Mb/s on your service — all are getting fooled. You may be getting more than 100 Mb from your home to the nearest concentration point. But as soon as your bitstream has to compete with many others then you can’t get your full speed. Say for example your 100 Mb gets mixed in with 100 others, that’s 10,000 Mb and that’s as much as most fiber backbone connections can handle. But you and 99 other neighbors are competing with tens of thousands of others all over the state and millions of others in the country. So you see how you’re not going to get the full speed that service providers claim.
I see this daily when I watch a low resolution video on YouTube and I get the spinning bagel waiting for the video to make it through the congestion. Another way that YouTube tries to get through the congestion is to lower the resolution. I start out watching at 720 but the congestion forces YouTube to drop resolution to 480 or even lower – 360 or 240, which is very poor – just fuzzy.
The system kind of works by depending that only a fraction of the viewers are streaming videos. But more and more viewers are loading down the system and it’s more likely there will be congestion and it’s less and less likely that they will get full speed. And it’s getting just slower and slower and more overloaded.