Well this is only an assumption, but I was on the #4 Cottage Grove bus heading north and there was someone using such foul language on the bus and I got the belief that it was used on children. It probably came to me because these little babies were crying. Not knowing what the language means but certainly by the actions of their mother who probably wasn't in a good mood.
When I got off the bus, I saw the mother and she had two children one in her lap another in a carriage. The messed up thing about this was that the mother was sucking her own thumb. I thought, heh, it's no wonder she's still a baby herself. She didn't look that much older she might have been a teenaged mother with two babies already.
I have a theory. She might grow out of it I would hope, but if you curse your children out and you did this consistently with utterly no respect for them then they may not know respect when they grow up. A teacher could tell them to sit down and be as polite as can be, but they wouldn't be able to hear that. You might literally have to scream or curse to keep their attention.
It could be more complicated than that, but I think it could explain perhaps some of my experiences in high school. Short of expelling students or suspending them sometimes polite suggestion isn't key to keeping control of the classroom. At the same time some kids you can talk to politely or without making sure that you use some words that they can relate to.
This should also go on the CTA Tattler! :P