On the highways here, the original speed limit of 55 was to save our nation’s resources, not just “55 to stay alive” but also it was an efficient speed to maintain and still pretty fast.

Inside the city it works much better to make drivers feel unsafe going fast. Narrower lanes, speed bumps, roundabouts, etc.

In answer to your actual question - some laws are just old and haven’t been unwound yet and others are used as pretext for profiling, police (or,n more properly whoever is running them) like to be able to stop people for no reason but that can be seen as illegitimate, so they keep laws that everyone breaks, jaywalking, etc to have an excuse.

I don’t think there is any one law everybody breaks really but also no person who has lived perfectly law abiding life.