Admittedly the English Language is a bitch to learn with all of our contrary rules, but the people who make the most mistakes with there-they’re-their are ones who were born and raised in it. Sometimes they’re double-digit-generational English-speakers.
It’s laziness, pure and simple. Lazy spellers, lazy educational system more interested in getting them in one end and out the other (I was a grade 3 teacher, I know) and lazy people who won’t mock and ridicule and ostracize the their-they’re-there abusers enough to make them see the light.
Let’s all take a stand a defriend anyone who uses them incorrectly on Facebook. They get one warning shot and then it’s “Sorry, Mom, your language skills are insufficient for me to warrant keeping you as a friend. Good-bye. See you for supper on Sunday?” .
Ciao for now.