Possibly the answer, Jacob, is that 'in the old days', people who wanted to use tools (and therefore sharpen them) would be doing so not out of desire for entertainment (i.e. a hobby), but out of a means to earn money (i.e. a paid job they would be doing day in, day out).
As such, the amount of time available for learning the skills (i.e. muscle memory) would be much greater, and also there would be a tutor/mentor available to indicate when those skills were not being picked up correctly.
Using jigs (however insulting you are of both those using them, and the jigs themselves) aids those (especially) hobbyists who do a little woodwork in their spare time and are keen to know that the main aim of enjoyment (cutting up wood!) is not being hampered by an inappropriately sharpened cutting edge. Yes, freehand maybe a little quicker (once the skill is learned, and practiced frequently), and certainly cheaper, but isnt always the best route for a user.
Cheers,
Adam