I used to believe what you believe. It seemed ridiculous that any other thing was possible. Then I spoke to an unusually large number of professional archivists who believe that given their limited funding digitization as a storage medium rather than a distribution method for a subset of the archive has very serious problems. Paper is actually remarkably resilient.
This isn't a question of technology. This is a question of archives, funding, and businesses.
I believe the fundamental answer is breadth. Breadth in formats, in storage methods, the more the merrier. Analog, digital, physical, the more different ways we have something archived, the more likely it is that the future will be able to access it. Archive video in every major video codec and at least one analog tape format as well. Don’t let perfection be the enemy of preservation, let it be but one tool. Especially with video, it’d be better to have the only usable copy of a work in 500 years be an analog tape, than only having digital formats available that may or may not be decodeable. There is no perfect answer, because it may very well be possible that there are also no working VTRs at that time, but with multiple formats you have multiple ways to access the content
Cost! Digitization efforts are barely funded as is. This is again one of those things that archivists would love to do but they look at their shoestring budgets and determine that other things are a higher priority.
This isn't a question of technology. This is a question of archives, funding, and businesses.