The meaningful number when comparing eg driving/walking to biking head injuries is not the absolute number but the fraction. If you’re 100 times more likely to get hurt when doing X compared with Y, it means X is inherently more dangerous/risky and warrants extra protection. Even if far fewer people overall do X.
I’m assuming here that far fewer people ride than walk/drive on your average day.
And the people who seem most discouraged by helmets are those who always want to tell you how discouraged everyone is by helmets. My experience is that most people who ride don’t really give a shit / are happy to have something to protect their noggin.
1000% agree we need better infrastructure. Separating bikes from cars should be priority number one and will have the biggest safety impact by far.