Exactly. Why the flip are we (the righteous cycling brother and sisterhood) beating ourselves up over this. To shamelessly riff a cycling great/arse/cheat, its not about the helmet. Its about the 1+ tonne of metal under the control of a human being depositing its energy into a fellow human's skull. For car vs cyclist, the helmet is a distraction, an excuse, a
MacGuffin. If this country's cycling safety policy boils down to "Wear a helmet. All will be well." then its no policy at all. Would you regard a cycle helmet as sufficient protection to step into a rhino enclosure. No? Why not? The cars that your helmet 'protects' you against weigh as much and go move faster than a rhino. Want a more scientific comparison? A car hitting you at 30mph has about the same kinetic energy as the same car dropped from about 2.5 metres (by my qualification-heavy but booze-addled estimate). That's a 0.9m cube of concrete or nearly 13 Bollos! Would you be happy to let that car land on your head if you could wear a helmet?
Much of the problem with road safety is the lack of appreciation of scale when it comes to the energies involved. For a driver, you can add or subtract from a car's kinetic energy by moving your foot a fraction of an inch, giving the impression that the car is a floaty, gentle thing. A modern car is designed to give this impression, but the energies involved are massive when applied to biology. A helmet can help reduce injuries from offs and skids, but an inch of polystyrene means nowt if you're hit by a car.
I did ask for you to make it stop!