This, and most users are just that, users, and not producers, so they value/pay for high download bandwidth and mostly don't care about upload. Upload bandwidth costs money, and not many will pay for it, so we get what we pay for.

This is changing over time as the aggregate upstream load from mostly passive users nevertheless becomes greater than a video upload stream, eg because people are face timing and gaming, etc.. so presumably we'll reach a tipping point where enough people have the excess up to support a growing set of always cached content. İ think this is the long game for distributed fileaystems, eg ipfs