If you are trundling along at 40mph in a 60 zone and I go to overtake you, why on earth would you speed up to stop me? I actually would love for you to travel at (or even just under) the limit, that would mean I wouldn’t be tempted to overtake, but don’t decide to do that as I’m overtaking. It’s not funny to then have to make the decision to either slam on and pull back in behind or try to go even faster to get in front. It is dangerous.