When’s the last time you corrected your spelling before anyone else did it for you? Or the last time someone pointed out a mistake you made in your mother tongue or adopted language?
Orthography, or the correct usus of a spoken language, is a modern phenomenon in Western Europe.
From the emergence of vernacular languages in the West (French, English, Italian, German, etc) and until the rise of the first modern Academies (the earliest being the Florentine Accademia della Crusca, founded in 1583), live languages weren’t subjected to linguistic control. No OED to regulate language, no Petit Larousse to sanction one use rather than another. Language was messy, it was rich and it was free.
Judging from the profusion of medieval manuscripts of texts written in a vernacular language (not Latin), where no copy ortographically matches another, lettered Europeans (and everyone else for that matter) didn’t really concern themselves with spelling.
The only area where correct spelling was crucial, though not particularly well-observed, was Latin, the artificial lingua franca of ecclesiastical, legal, scholarly affairs. The artificiality of a language learned exclusively from textbooks following strict rules had a huge impact on all other languages, once the latter approached a similar level of authority by being written down and copied again and again.
In other words, the use of Latin as a non-natural language in the West led to a laying down of equally strict rules to all other languages, kickstarting a linguistic approach to languages which had previously been excluded from the community of letters. What began as philology (the study of classical languages, i.e. Greek and Latin, but especially Latin, ended in linguistics, a discipline and area of research which had a lot to say not just about language, but about us as well.