Every so often on social media I come across a raging debate about how many spaces belong between sentences, one or two? In school we were taught two. In college they teach one. Flaming wars ensue!
So which is it? The answer is both generational and technological.
In the days when typewriters were monospace, two spaces were necessary to distinguish between sentences. So all of us who learned to type on IBM Selectrics (or Royals!) have built up the muscle memory to thump our thumbs twice.
When magazines and newspapers began typesetting using proportional fonts, they specifically started using one space to allow them to fit more text in a column.
If you just can’t break the habit yourself, you can still type in Microsoft Word with two spaces, then do a Find and Replace and replace <space space> with <space>.