Any statistics purporting to show a similar head injury potential, per mile, for cyclists and pedestrians are suspect. One, we don't have good mileage data on those two groups. Two, most pedestrian fatalities that involve simple falls are of very elderly people.

This is in contrast to injuries from falls from bicycles, which by definition are of younger people, and are at a faster speed than walking.

I personally know of two people who were saved serious head injuries in bicycle accidents by their helmets, and I am pretty sure I was saved from a concussion in a fall I had.

Certainly helmets aren't going to help in some kinds of accidents, but they help in quite a few.

If you want to run the risk of being helmet-less, don't kid yourself that it's actually as safe. It is an additional risk to run.