Yes, I think it's lack of knowledge and laziness. When I used your and its without their other parts it was because I didn't know any better. I didn't know when to use it's and to be frank I knew about you're but I could never remember how to spell it or when to use it either ha ha.
When I was learning to write I kept forgetting how to spell is and are
.
My dad made me feel better though because he forgot how to spell "a"....so the conversation went like this:
Dad: how do you spell A?
Teacher: A?
Dad: yeah.
Teacher: A.
Dad: ...yeah how do you spell it?
Teacher: A.
I believe he threw a tantrum lol.