I would go further, and suggest that people who knowingly speed do so again because of the psychological reward. If you break a rule on purpose, and there is no negative result, meaning you got away with it, the implicit reward means you feel a tiny bit better than you did before. You're beating the system, sticking it to the man, or something like that.
And if it is easy the first time, it will probably be easy the second time, and the third time, and the fourth time. The cumulative effect of tiny rewards is to embed behaviour that diverges from the original expected behaviour. Speeding, swearing at cyclists, driving through red lights.
When you reach the 853rd time, and you're speeding as usual, your expectation is for there to be no repercussion. Then a child runs out in front when you happen to be looking down at the phone and you realise your foot is caught under the brake pedal.