Earlier quoted context omitted.
Resolution isn't an indication of image quality. Just like megapixel chasing in photography. Sure it's 4k, but it's heavily compressed, just like the terrible audio quality you get still to this day. They aren't streaming you 100GB.
have you run 4K video through things like Handbrake? They've been proven to seriously reduce the amount of space (and, therefore, bandwidth) that video files need, and considering that 4K videos have about three times the resolution [1] they have a lot of space to gain from it. I would guess that there are appliances that can run some flavor of compression in real-time to get 4K to stream well. Yes, it will take more…
However, that means nothing for live streaming as generally speaking "live stream" compression really tends to suck a lot. And as to the above, a lot of devices don't do well with 4k h.265 streams for playback, but getting better.
Also, I really don't think I'd notice going from 4K to 8K for home video, maybe for some gaming, but even then I'm doubtful. Also, I'd expect 8K gaming on even next gen's console to be closer to Wii model quality than what we see in 1080p gaming today.