That's also partly due to Netflix' extreme web market share: They account for ~31% of all global aggregate internet usage, and combined with Youtube, the major video streamers account for ~43% of all global aggregate internet usage. That's probably because their business models necessitate a lot of traffic, since content needs to be re-downloaded on each viewing/listening.
Well according to xtracto's link, Netflix is only 0.85% (and YouTube is 5.7%), so I don't think numbers can be compared across sources - the methods of measuring traffic seem to vary wildly.
