[II2II]

While it's true that none of that prevents computers from replacing typewriters, it becomes more difficult to convince people that computers are better than typewriters.

Put another way, I grew up with those 8-bit machines. I preferred using those 8-bit machines for writing since it was easier to edit documents, which was important because I was young and learning to type (along with learning spelling, grammar, etc.). Using a typewriter wouldn't so much be an exercise in frustration as it would be one of mental anguish. On top of that, I wouldn't have the expectation of screen text mapping reasonably well to the printed page.

On the other hand, people who had experience with typewriters (or even 80-column terminals) would have that expectation. And they would be bumping into that mismatch whenever they were dealing with indenting or centering or lists or any number of other layout options. They would also be more accustomed to the writing/editing process with a typewriter, so they would be less inclined to view it as problematic. The flip side is that they would be unaccustomed to the writing/editing process on a computer, so they would be more inclined to view those quirks as problematic. On top of that, the process of using a word processor would be completely different from using a typewriter. Think of over-typing: (fake) bold, underlining, and so on. It is less labor intensive to do on a computer, but the average secretary would have trouble seeing that when they have to navigate the then cryptic user interfaces of software.

Proving that something is possible probably wasn't the issue here. Proving that something is better, which isn't hard to do even considering the primitive word processing software for the Apple II of that era, isn't the issue here. Dealing with the expectations of people is.