On typewriters all characters are the same width, typically about ½em wide. Some of them compromised their hyphen so that you could join two of them together to form an em dash, but a good hyphen is closer to ¼em wide. But that compromise also meant that a single hyphen would work very well as an en dash. And generally hyphenation was not very important for typewriters because you couldn't produce properly justified text on a typewriter anyway, not without carefully preplanning each line before you began to type it.

Computers unfortunately inherited a lot of this typewriter crap.

Related compromises included having only a single " character; shaping it so that it could serve as a diaeresis if overstruck; shaping some apostrophes so that they could serve as either left or write single quotes and also form a decent ! if overstruck with a .; alternatively, shaping apostrophe so that it could serve as an acute accent if overstruck, and providing a mirror-image left-quote character that doubled as a grave accent; and shaping the lowercase "l" as a viable digit "1", which more or less required the typewriter as a whole to use lining figures rather than the much nicer text figures.