Ok I REALLY don't want to get into this discussion, but I can't tell if you're being serious.
In case you are...kids don't naturally become rude, they learn it from their environment. If parents allow it, it will continue. If parents lead by example and correct poor behavior appropriately, kids will act right. It's called parenting. Rudeness isn't organic. It's taught. Or allowed to happen. Maybe kids will be fine until they learn it from their peers or other adults they spend a lot of time with. You tend to act the way those around you act and if they accept or encourage bad behavior it will continue. If they don't accept it and instead stop it, well, it will stop.