I don't get why it's so hard to believe that people don't speed.
Really, you should be glancing down at your dash every few seconds (I won't put a number on it, but every decent driver will know what I mean) to not only check your speed, but also to check on temp & press gauges, along with other warning/info labels. Doing that, and having relatively basic throttle control, means it's virtually impossible to speed unintentionally.
It's not a case of staring at the speedo, nor saying that everyone does it so it's okay, it's actually perfectly possible not to speed ever. Its a conscientious decision in the vast majority of cases, whether that's because they want to go fast or because they're not paying any attention to the dash because they can't be arsed.
The worst thing to claim when you're speeding is that you didn't know speed you were doing. That's just as bad as staring at the dash all the time.