There are a lot of videos that I'd like to watch in UHD and/or HDR but there is no streaming service that provides them. Why is that? Why do they not release them in UHD? The cameras they are shooting it with are more than cappable of providing UHD.
Just because something is shot on film doesn't mean the video files produced have been mastered for UHD/HDR. That's a level of processing that still has to happen before it reaches the consumer.
If a film has already been mastered for DVD, it has to be re-done for Blu-Ray, and re-done again for UHD/HDR.
Not all films are popular enough to justify that repeated processing. "Ah, DVD looks fine..."
Plus, a lot of companies don't bother going back to the film when they do rereleases. A lot can't due to all the post processing and special effects dome digitally. So most upres'd releases make significant compromises in one area or another, to the point where for some you can have better quality just stretching the video and using some shaders.
One classic example being the Babylon 5 TV show... They thought ahead enough to film all the live action in widescreen, but all the CGI was done in 4:3 for expense and rendering time.
Looked fine on TV in the 90s, not so much on DVD/Blu Ray. But short of re-doing all the CGI from scratch, not much else they can do.