Is it only fatties though? Common, similar spelling mistakes also include break and brake, definitely and defiantly and many more. There may be some correlation between fatties and lower education levels, probably due to a generally lower income, but correlation doesn't necessarily entail causation: https://xkcd.com/552/ I have to admit that I also used to use  loose instead of lose, although english isn't my native language. In recent years spelling mistakes have also gotten a lot more common in my country, because of regionally differing education that in some states puts a lot less emphasis on proper spelling.  In those cases, children are taught the alphabet first and are then told to come up with a way to spell words on their own. Afterwards, they may learn the proper way to spell the word, although sometimes it takes YEARS for them to be taught the correct spelling. As you may imagine, things have gotten so bad that the average bachelor thesis now contains around 10 spelling/grammar mistakes per page, although this already includes students who were never taught this way...