This “feature” accomplishes nothing of value for anyone, including the streaming services, but imposes a massive (and for most people, confusing and frustrating) hindrance on honest people simply trying to easily capture high-quality (as opposed to, say, using their damn phone to take a photograph of their reflective laptop display) screenshots of the shows and movies they’re watching.
This is the reason I stopped using Netflix and other streaming sites in the first place. It would intentionally black itself out whenever it thought something might be reading the screen, or whenever I used a monitor it didn’t like. It was literally easier to just find what I wanted on a piracy site.
This doesn’t even stop anyone from recording stuff illegally. An hdmi to usb capture card is like $20 on Amazon.
Also god forbid anyone take screenshots of shows to share with their friends. Imho this “feature” has been detrimental to all parties involved, including the streaming sites. They’re just too up their own asses with copyright protection to notice.