From a guy who learned, in high school, to set type and print pages the old fashioned way, with metal type. It was retro even back then. But what an art!
From my perspective the very concept of a typewriter-style space is an abomination wrought upon printing by the typewriter. Of course, typewriters were tremendously useful devices. I have no quarrel with them other than that.
Spaces in the retro printer world: There's this concept of the "em" or quad space. It is a square hunk of metal the same height as the letters in the typeface. We still have it in   and css rules like line-height: 1.25em;
We had five kinds of space in the lower case of the typeface. The "case" was a tray with dividers. If I remember right, they were
-- em (quad)  
-- en (half a quad)  
-- thick ( ~ 1/4 of a quad) the ordinary space and in most fonts.
-- middle ( ~ 1/5 of a quad)  
-- thin ( ~ 1/6 of a quad in most typefaces)
-- numberspace (the same width as the numerals in the typeface, an early nod to
for tables.Notice that the precise widths of the thicks, middles, and thins are determined by the typeface's designer. Then and now.
Our teacher told us to set up body copy with thicks between words.
We then justified each line manually by putting two thins in place of a middle to add space, or one thin to remove space. Choosing where to adjust the space was an art. It was good to avoid rivers of space running down the page. (Adobe InDesign gives enough control to do this; I don't think other programs do.)
AFTER SENTENCES, we used ens for most copy, and ems for poetry and that sort of thing. I am pretty sure the two-space typewriter convention grew out of printers' ens or ems after sentences.
In the 21st century digital typefaces have contextual glyphs. That makes it easy for the FONT DESIGNER to choose the default spacing between sentences. That's as it should be. The rest of us should pass dot space to the font. The font designer "owns" legibility.
I, for one, have had a heck of a time unlearning the dot space space sequence I learned in high-school typing class.