I have had accidents on both bikes and motorbikes and I think a cycle helmet has little effect if you are in a collision with a car when it comes to impact injury. But from experience I know a bicycle helmet can prevent gravel rash.
Impressive picture Steve! Glad you're all healed up (assuming the profile pic's more current) x
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Yes, helmets are good for minor injuries - abrasions, bruises, minor cuts. These can be unpleasant (and tend to bleed a lot more than similar on your elbow/knee), and I don't blame anyone for mitigating those impacts.
But they're not life-threatening. I've crashed my car and spent
considerable time in hospital. Also had a head-injury on my bike (stitches, couple of hours total in hospital - driver prosecuted, large payout from his insurance company). I'm happy that I know what I'm talking about.