We bike on the shoulder of a 50+mph 2 lane highway if one of those texting drivers doesn’t look up in time to see they’re on the shoulder and headed right for me my helmet won’t do much for the broken back I’ll probablly get when I’m hit from behind at that speed.
But that’s not why I wear a helmet, I wear a helmet to protect me from me. If I hit a rock or swerve from hitting a muskrat or a goose or swan charge me I want to be protected when my head hits the pavement. We also wear helmets in the campground for the same reason. A rock or a stick can take us down at any time.
I should probably be wearing a helmet cutting the grass.