I didn't go through more than 5 or 8 minutes of the video but it sounds to me like an updated version of V-Mail that was popularized in World War II.
The concept may be good in theory but there are still those people that either do not have internet access, are not computer literate, and/or do not wish to be (i.e. seniors, persons with disabilities such as bad vision) that limits their computer use, that will always make a delivered piece of mail more valuable than an electronic scan of its contents.
There is also the human factor of one desiring an original document in a person's handwriting or with a person's original signature on it, where an electronic copy just won't do. And then, of course, there's the price, as I expect it just won't happen with the current postal rate structure now in effect.
I'm sure there is a litany of other reasons that would need to be ironed out as well.