[apgwoz]

The impression that I got was helmet laws make people feel like biking is default unsafe, which leads to less bikers, which leads to less visibility and less isolation of bikers (no demand, no tax dollars spent on infrastructure).

If you want safe biking, you need visibility and isolation. The visibility here is helped by, say, biker wearing blinking lights and reflectors. But also, just having constant presence of bikers on the road such that drivers get used to sharing it. The isolation is space between bikes and 3000+ pound hunks of accelerating metal, e.g. dedicated bike lines / bike barriers.

[taeric]

This is somewhat comparing the wrong metrics. The more people you have not driving a car and instead on a bike, the safer everyone is. Exactly like the more people you have out of a car and on a bus.

The bus is an easy comparison, as even on a bus, you would be safer with a seatbelt. But the added danger of not having a seatbelt is more than offset by the reduction in cars.