I know I'm coming very late to this, and I've picked a post more or less at random to reply to. I appreciate there might be a link between helmet wearing and the view of politicians. But I suspect the correlation is weak, because policy is rarely made by evidence, it's made by pressure groups and emotion. Politicians are human like the rest of us, and they respond in human, irrational, emotional ways.
Yes, there are exceptions - seatbelts and motorbike helmets are possibilities (though it would be interesting to find out whether the emotion or the evidence came first - I suspect they were contemporaneous).
My best guess is that the success and the safety record of the Boris Bikes in London - in particular their success as a tourist attraction - has squished a mandatory helmet law for the foreseeable future. Any attempt to bring one in can be met with a simple statement - "You'll affect tourism." It doesn't have to be provable, as long as it's plausible.
Seatbelts and motorcycle lids do save lives. There is overwhelming evidence in both area's.
The early seat belts were just buckle and strap lap belt affairs, then the 3 point harness, crumple zones, collapsible steering columns, seat belt pre tensioners, then drivers and side air bags...the list goes on and on.
Motorcyclists also get very well looked after with safety gear. The market for this is nearly as big as the market for the bikes. The vast majority of bikers I know do not ride on very hot days if the gear is too hot to wear. It is called
AGATT (All The Gear, All The Time) because the prospect of getting it wrong isn't pretty....you don't see many bikers who have binned it going back out without better quality gear they crashed in unless that gear did its job properly.
I used to ride in trainers, jeans and a a leather jacket. Sure you can get away with that up to about 20mph (still going to scar) , but beyond that...no it really hurts even with leathers on.
Because bikers have compulsion, they are also voting with their feet, and demanding the best which the biker clothing/lid industry can offer. This in turn means that the money is there to continuously improve the quality, and that means the odds shift just a little bit in their favour..one always hopes than they will never need the gear, but that in itself is playing the odds.. none of us know what is around the next corner and that is why when mixing with people on the roads who care less about my life than I do, I always buckle up, and at the very least always use a lid...