There are about 300,000 injuries per year as a result of falling down stairs, and about 19,500 to do with cycling.
Given that, at a converative guess, 95% of the population use stairs at least twice a day, whereas only 10% of adults cycle at least once per month, I'd suggest that the risk of injury per ride is significantly higher than the risk per go on the stairs. And when those injuries do happen I'd suggest they are more likely to be serious.
Let's just take 10% of the stairs figure then - that's 30,000 which is of course much less than 19,500. I'd suggest that falling down stairs is likely typically to be massively more serious than the usually minor injuries from the statistically very safe activity of cycling.
Going back to the OP, paramedics see the superficial effects of accidents involving heads*. The people who see the real damage are neurosurgeons, and the last time I saw anything from them they were of the view that helmets were at best useless.
What makes all cycle helmet discussions and opinions totally useless is the complete lack of any rigorous research. Statistical analysis, often quoted by
@User does however show that there is no overall benefit or disbenefit from their use.
*I am fully aware that helmets do of course provide totally effective protection to the parts of the body most often damaged in cycling accidents, including eyes, hands, elbows, knees, spines and feet.
