The 37% is accurate for peak usage. What makes it more complicated to measure is that Netflix and Google have private networks, CDNs that are uploading all of that data during peak usage, which is much closer to the user geographically. They've basically spent billions of dollars to unclog the internet backbone already.
They occupy 37% (trusting the source) because that's how much people want to use their service, not because they force themselves on "the internet".