I have to carry around a helmet- yes I find this burdensome. Real estate is hard to come by in NYC- and my commute requires a partial subway commute. When I rode a motorcycle to my job and had a cube I was annoyed by the MC helmet, but felt the risk tradeoff was worth it and could at least tuck it away. Now I am subject to the hideous open office trend, it would be a PITA. Its not the weight, its the volume, and the fact that I would have to redo my hair once I went anywhere, all to prevent an event that seems about as likely to me as winning the jackpot on a scratch off ticket. Seatbelts don't bother me at all, they are built in to the car.
Still my point about a drinking helmet stands- drinking is a dangerous activity- 60% of all hospital admissions for head injuries involve alcohol. Clearly we could reduce the severity and incidence of these injuries with helmets. It would be interesting to see how many "drinking years" it would take on average to get a head injury worthy of a hospital admission.
Driving is dangerous too- and in virtually any accident it seems likely your head is going to come into contact with something- even if it is an airbag, and the mv^2 is much higher- we could reduce the severity and incidence of head injuries if everyone wore a helmet, especially an NFL style helmet with a faceguard...
And you accept that wearing gloves is ok, but you don't wear a jacket- so you know you may fall, and possibly scrape along the ground a bit, but you don't wear a jacket that most motorcyclists consider to be basic standard gear.
Do you understand where I am going here? You assess risk a certain way and make tradeoffs in what you are willing to do to protect yourself, as do I. However, what your risk assessment has determined wearing a helmet as necessary and foolish not to, I see as just another unnecessary burden, choosing instead to wear armored gloves in winter, and accepting other risks. You may feel not wearing a helmet is something a fool does, but my years of riding have given me intuition (in other words, my developed common sense) that the head is highly unlikely to be injured, and statistics back me up on this.
If I did a lot of high speed road cycling, it would probably change things, but my rides around town where I top out cruising around 15mph and if I go down a hill hit 30 for a brief minute or two, its just not necessary or reasonably useful.
So wear your helmet, but I feel denigrating those that don't because your "common sense" tells you its necessary is misguided and somewhat ignorant.