Typewriters were monospaced, which gives you extremely limited scope for distinguishing hyphens and em dashes. Small wonder that they didn’t bother attempting a distinction, and then that provided the inertia for us to never get such a thing now.
Typewriters are a lowest-common-denominator sort of thing. They lacked all kinds of widely-used stuff, and some of it they killed by their omission. Accented letters you mostly couldn’t do at all, and the rest of the time could only do by a terrible hack.
There’s a similar story in the final death of the letter thorn (þ) in English <https://en.wikipedia.org/wiki/Thorn_(letter)#Middle_and_Earl...>: imported fonts lacked the character, so people substituted it with y which looked most similar, and that substitution became ubiquitous, and now most people think the first word in “Ye Olde Curiositie Shoppe” is pronounced /jiː/ (“ye”), whereas it was actually just how they spelled “the”, so it was /ðiː/.
It’s a general rule in such technologies: although they make many new things possible, they also damage what was there before.