on half-wearing helmets and weirdness

One of the strangest phenomenons that I come across in the cyclist's behaviour is the cyclist who rides around with his/her helmet somehow attached to the bike or their backpack, instead of riding with it on their head. In Victoria I see this all the time and I just can't for the life of me make any sense of it. It's kind of like remembering to bring a gun to a gunfight but insisting on fighting with a spoon or something. It's bizarre. Now I know there are people out there that will tell you that studies have shown it's actually safer to ride without a helmet than with one. I think what they're trying to convey with those studies is that a person driving a car will give a person that does not wear a helmet more room, and respect than they will give a rider in full kit. I'm sure this is true, since the driver probably reasons that a rider in full kit will sort of know what he is doing and therefore it's okay too speed by him with only inches to spare. This is nonsense of course, but I can see that this might be the case. Nevertheless, if you're riding around with a helmet in the first place, why not store it on your head? It's not only the most logical thing to do, but it also kind of helps out if you crash and hit your noggin and not to mention that helmets are super awkward and annoying to carry in other places than your brainpan. I'm the kind of rider who hates rattles and squeaks and unnecessary junk on my bike. I could not ride with a u-lock dangling from my handlebars. I can't really use racks and panniers either and I certainly cant ride with my helmet flapping on my handlebars. But even if I did not mind all these things and rode around on a squeaky, rattling hulk of a bike I'd still wear the helmet on my head. Not doing that is so stupid that it boggles the mind.