An hour long 30 Mbps 4k HDR+ video file will be roughly around 10-15+ GB with H.265 encoding.
As others have pointed out, a well encoded 720p or 1080p video offers a decent enough viewing experience quickly at far, far smaller sizes than a 2k or 4k videos (file sizes will be 10 to 20 times smaller at these resolutions). Note also that some pirates encode videos with the CPU, than using hardware encoders, and thus these videos tend to have a higher quality with better compression (hardware encoders, while blazing fast, tend to do a poorer job than CPU video encoding). Thus, these smaller sized video files don't require high-speed internet, can be downloaded fast and also encourages people to save the videos longer. This allows some to create their own personal video library. So a side effect of this is that people store and share these videos longer, and their smaller sizes now allow streaming torrents of popular content. Some torrent sites today have even started offering this through the browser itself - so non-techies now don't even have to download any torrent software and learn how to use it. That's near-Netflix like convenience, with more content, for "free" - and that's what these services are up against.
We also can't ignore that 4k videos are often only available at higher tier subscription plan. So even if Netflix, or other streaming services, think that some of these people can be enticed to subscribe to their services, with their high quality 2k or 4k videos, they will have to offer them at a lower price to beat the "free" model of piracy. (It's very hard to compete with "free" - just look at Google search engine's market share and its non-free competitors' market share to understand this).
All this is of course irrespective of the fact that 2k and 4k resolution HDR+ videos are also increasingly available now a days on torrents too.