Despite this comment's dubiety, this is a good point. Text communication is only about 8,000 years old IIRC, which is quite recent in human development.
You can knock off a few millennia there, and if you want to include most of the population, barely a century or two.
Literacy was needed to read the Bible and operate machinery, and now we have videos for that. Only (some of) the video makers need to read, so they can raid the libraries for material.
