There is also an unwritten "grace" that is given in many areas, where you don't ticket someone until they go 10 mph above the speed limit. To get a ticket for going 34 mph in a 25 mph zone usually means you angered a cop, you were doing it in bad weather or at some other time when it was unsafe, or you wandered into a local town's legal extortion racket--excuse me, speed trap.
It is constitutionally questionable because of vagueness and due process, but it's still how driving works in a good part of the United States.
I've done quite a few ride-alongs with my local PD, and almost universally, for the officers not dedicated to traffic enforcement, they couldn't care less about run-of-the-mill speeding. They would home in on people doing so supidly/unsafely instead, or going way over the limit. (Me: "that one was 15 over" Him: "nah, just wait, we'll get one doing 20-25 over")