Law enforcement attracts psychopaths with power issues.
Well, that's an extreme, most of the real head cases can't pass the psych evaluation, but just because they can't be the cops they want to be it only winds them tighter.
What draws most normal people to be cops is the speeding.
Imagine putting your foot down, so that you can cruise at 70 all day long, even through school zones.
You're aroused a little right?