A good portion of those people we've banned more or less subconsciously anticipate being banned at some point. Follow with me here for a sec: Communication begins in the head. Whatever a person intends to say or write is all pre-meditated to some degree in their head. They just have to fill in the details from Point A to Point B, etc. It is at that stage where the voice of conscience speaks up in their heads, too, and that voice usually says either, "That looks like a well-thought out response on my part! A good quality post!" or "This'll probably get me raked over the coals or banned!!"
The bottom line? Simple -- those people we've banned had that latter thought float accross their minds just before clicking the "Submit" button ... and didn't care. They clicked "Submit" before the voice of reason could pipe up! And they continue to ignore that voice even though the "EDIT" button is staring them dead in the face. These people are usually given so much rope here by us that -- true to the old adage -- they eventually hang themselves with. So, instead of arguing/proselytizing to them ... we just oblige them!!