Probably it is the regular long commute and that most of time nothing happens. It is long, people are bored daily and impatient. Some won't get free time after they come home.
So they push boundaries progressively getting comfortable with more and more risk. Because there is no negative feedback and nothing happens. (Until it does).
Absolutely. To answer your question, both. I think people realize there is some inherent danger, but don't care. Partly because of the 'itll never happen to me' thought, and partly because humans have been driven to isolation so much as to see other drivers as not human, but merely obstacles. Depressing truth.
I honestly think it should be treated the same as driving while intoxicated (in my state it’s just a fine which I believe does nothing to deter people).