In addition to voice recognition and those choices you left out -
You left off "so busy doing eight things at once that these sort of mistakes happen more often in an informal forum than for formal documents."
If someone talks to me (often occurrence) while I'm typing, I'll transpose the spelling of what they just said vs. what I intended to - happens a lot.
And - English is not everyone's first language, neither is typing it all out an equal skill.
That's why we allow gentle, well-intentioned corrections if both parties are cool, but otherwise - site rules say no spelling or grammar police.
We all make missteaks.