Those are all EXCELLENT points! Back in the 1800's(and even up into the 1900s) many children in the US were barely educated due to their parents needing them to work on the farm to maintain the families already meager income level.
There is also a factor of self worth involved where someone with a lower self worth will usually be more ready to accept someones talking points as facts without verification(which leads to myths/legends.) I expect(though I have no evidence to prove!) that a group of people who are essentially slaves will be more open to believing things without verification than those who are allowed to earn and keep the fruits of their labor. I believe that a sense of accomplishment pushes one to more readily question the status quo, which is a prime motivation for dispelling myths (or attempting to anyway.)