You have a point. It's been a while since I drove a pickup and it had a good view out the back window, but I know many pickups don't. I've never driven a semi though I have driven a U-Haul many moons ago.
I think it will be a long time before a requirement for some sort of passive rear view device is eliminated. If the car looses the electrical system, the mirrors and back window don't go opaque.
In truck driving school and truck driving instruction manuals, they say not having rear view ability through the rear view mirror and the rear window is a deficit that truck drivers need to get very good at overcoming, and in addition, they teach us to learn about and mentally map all our blind spots and what's in them (probabilistically) and never to underestimate their danger, and always error on the side of caution. They say you have to show mental proficiency in remembering a mental map of what's in your blind spots at the same time as knowing when to get out to make sure you have verified there's nothing going to be in them or something you don't know you need to know. They say you can use your own eyes or get assistance from someone else.
I agree with what they teach, require us to learn, and test for (when they're doing it right, which the good schools do).
Therefore, I simultaneously agree it's possible to drive without rear window view, but that it's not the same thing as, ease as, nor danger level as having that window there. I'm just trying to inject a little sanity into the conversation.
But, I want a completely windowless car with only projected camera displays, so I'm certainly not a full window purist by any means. While my main application is a home with wheels, I think that is kind of irrelevant to the discussion.
In the future many spaceships will have all of these questions going on too. Um, actually, probably already been an issue since the beginning of space travel engineering and currently still. Probably any vessel has these issues. Big boats use computer screens to drive through water. Not having a rear view window or having it I think is part of a larger navigation and steering engineering issue that has lots of solutions.
I'm extremely open minded on this issue. But a free for all it ain't. Whatever solutions are made, and I'd love to see interesting new solutions, have to be completely cogent, by which I mean completely functionally safe within the parameters needed. I let the imagination reign, engineers engineer, and the testers test (with a lot of those people being the same people by functional necessity).