1) They've discovered that the cops won't bother to pull them over for such things.
2) They found that the cops are too busy elsewhere, and unless one sees them doing it, and are not busy with chasing someone else, they can get away with it.
3) They are goal oriented, focused on getting where they want to go, and everyone else is just in their way, like obstacles in a computer video game that they have to dodge to reach their destination as quickly as possible.
4) They think that "Only the strong can break the law".
5) They own an expensive car, and this makes them more important than other drivers, who should get out of their way and never mind the traffic laws. (see 4)
6) Their wife is about to have a baby and they are rushing to the hospital.