I understand that's the way it's programmed, I just don't understand why.This is one you shouldn't blame on computers. This goes back far before that and the brand name on the machine was 'Linotype'. The output was called hot lead type then. Later it became photo typesetting and today we call it proportional fonts. It's how magazines, books, newspapers and catalogs were printed back in 'the good old days', and why your typewritten Courier 10 pitch space-and-a-half just never did look the same. Those professional systems were set up to automatically space words a correct distance apart and sentences a different distance apart. Spaces between letters were also set (this is called kerning) so that an A and Y are closer together than a pair of Ms. There was a big division between those people who just used typewriters and the professionals who worked to make their craft an art form.
Today, computers allow people to look much more professional than ever before, but it gives many users abilities they don't (and often never did) understand or know how to control. The system will still make what you output look as professional as a modern magazine, but you can't work by the old typewriter rules to get that. Then again, you never could!
Having said that, some of you may remember that I'm a big proponent of plain text. Perhaps I should explain why. Plain text is pretty basic and universal. I can send it to someone else and I think it doesn't change because it will come back to me the same. But the truth is, if the recipient has their preferred system font changed to something else, it *does* look different on their system. Someone with visual limitations may have their system set for a preferred font of 14 point Roman Bold, while someone younger may prefer the clean look of 10 point Arial. Plain text allows people to use their own system preference to read messages without imposing that on others.
In many ways, that's a good reason for archives to be in plain text. Everybody can read them in a display tailored for themselves. I've always believed that if you have something worth saying, you don't need typographic enhancement to make it better. If you need a picture, draw a picture, but if you're writing, use words in a format the reader finds comfortable.
That's not to say there aren't pitfalls in plain text. Too many systems are set by default to use paired double or single quotes. You've all seen them - they often look like curved tadpoles, and the close quote is almost the inverted mirror image of the open quote. But plain text sees them as different ascii characters and they often come back as code. True plain text needs the single and double apostrophe like typewriters use ( " or ' ) to avoid defaulting to code. A good typeface translator would catch these error and make the simple conversion, but there are damn few of them in existence.
Before you condemn modern typography because it doesn't follow you old typewriter rules, understand that you were taught what you needed for the equipment you had. Today you have a refined typesetting system many generations of printers would have paid huge sums for. Don't complain that it doesn't drive like a tractor if you want to be driving an auto.