As someone with a foot in both camps I think its more an issue of many drivers just not reading traffic/road conditions ahead rather than not knowing how to opperate their brakes, in fact there seems to be an over-reliance from the majority of driver on stamping on the brakes at the very last second rather than actually preparing for upcoming cyclists/traffic/corners/etc by letting the speed drop off and gearing down earlier...
I'm not sure it's even about speeding in many cases but a sort of "digital" attutude to contolling a car; you are either accelerating or braking as hard as possible, there is no comprehension of any sort of middle ground....
There's nothing wrong with overtaking on a clear section of road where you know yuo can get past some doddering fool cleanly but by the same token there's certainly no shame in hanging back from those "50/50" overtakes with partial visibility for oncoming traffic...
IMO the difference in arrival time between driving the same 20mile route (along single lane A-roads) in a more relaxed manner Vs applying a disproportionate sense of urgency is probably about ~15seconds max, I see the same nobbers burning an extra £2.37 more fuel along the same stretches of road as me most days and the net benefit is being 1 car ahead at the next set of lights...