The best YouTube downloaders, and how Google silenced the press

This seems to be starting with the assumption that it's possible to prevent people from downloading the videos. That is a false assumption. You can, after all, just play the video and record it. Even if the entire machine playing the content is flawlessly locked down, you can just record the output.

The efforts at DRM done by companies like Netflix is done because the companies that licensed the content demand it. That doesn't mean the DRM works. You can find torrents of all those shows.

Why 4k shows are still quite rare on torrents?

Hard to speak for everyone but I'd not be interested in them because it's a lot of storage space and my device can display only "1k" (1080p) anyway

1080p is 2K. The value of the "K" coefficient is determined by the x axis, not the y axis. That's why 4K is 3840x2160.

16K = 15360x8640 8K = 7680x4320 4K = 3840x2160 2K = 1920x1080 1K = 960x540

(Every value is a doubling of the tier below it, or in the case of "1K" a halving.)