“What is so ambiguous upon providing limited protection for your skull in the likely event of an off when mucking about on mountain bikes, let alone low hanging branches.“
Well, the OP was talking about the road, not mucking about on mountain bikes. The likelihood of various scenarios differ quite markedly between the two. The sort of mountain biking that most people on here would indulge in of a weekend is the sort of stuff where you’ve got a pretty high risk of getting into an incident where a helmet is designed to provide benefit. An experienced and cautious cyclist on a rural road, on the other hand, probably has negligible risk of most incidents; the most significant perhaps is being wiped out from behind by a car travelling at high speed, where a helmet is likely to be well outside its designed parameters. Equally, for a family jaunt round some quiet fire roads there’s probably less risk of a fall than there is whilst, say, jogging.
There are less obvious factors as well. There is evidence to suggest not only that (for whatever reason, and the cause/effect may go either way) unhelmeted riders may be less likely to have an accident, but – perhaps more significantly – that motorists are more likely to give unhelmeted riders more room, thus reducing the likelihood of an accident. (And I’m sure we’d agree that avoiding an incident is preferable to being involved in an incident which is of a severity and nature at which a helmet makes a substantive difference to the outcome. (Remember that for any incident which is too minor or too severe for that to be the case, there’s no safety benefit to wearing a helmet – the thing of course is that those boundaries are virtually impossible to identify accurately.)
There are numerous peripheral things not related to personal safety: such as whether you think helmets propagate the perception of cycling being more dangerous than it really is; whether you find a helmet a bit of an annoyance; whether you’re implicitly going to accuse all Sikhs of having a cheap head. Trivial in isolation, but they add up. Personally I find the rare occasions I ride without a lid are more pleasing because of it – in no small part, cycling’s about freedom.
(And yes, I always wear one for ‘proper’ off-road rides. And always for commuting. And usually for weekend road rides – sometimes for slow rides on dry summer roads I indulge in a bare head. But very rarely for popping to the shops, for touring, or for family pootles round fire roads. Yes, there’s always the outside chance I’ll find myself in an accident where I wasn’t wearing a helmet, could have worn a helmet, and the helmet would have made a real difference… but that combination seems far more likely to arise when I’m not on a bicycle than when I am.)
On which note, I’m going to go to bed, and try not to trip on the stairs and bang my head on the wall whilst doing so 😉