Are you going to not wear helmets while you wait for this mythical no-risk infrastructure? Where is this nirvana that causes you to skip a helmet on occasion? Even if there were a system of bike paths with no possible car contact, there would still be accidents and head injuries due to equipment malfunction - yours or a nearby rider, errant wildlife, icy pavement, etc. I have a kid alive today because he wore a helmet on a quiet country road with no car in sight, but difficult to detect damage to pavement from tree roots in shadow that caused his bike to flip end over end downhill.

Protecting yourself with available safety equipment should be every rider's first priority in the real world. You can get pretty banged up waiting for perfection.