It follows that the most important thing that can be done to increase cycling's share of the transport task is to make it safer, and be seen to be safer. It doesn't matter that cycling is already safer than driving - most people's perception is that cycling is more dangerous, and it's the perception that must be addressed.
That's the main reason helmet laws are bad news, because they promote the idea that cycling is dangerous, putting more people off. A lesser reason is that some people don't ride because they don't like helmets, but that is probably not the worst thing about mandatory helmet laws.
Perceived safety is why separated bicycle lanes (e.g. Swanston St north) and off-road bicycle lanes (e.g. along the Yarra River) increase cycling so dramatically.
So we've covered the main reasons putting off potential cyclists. What are the reasons making people want to cycle? They are many, getting fit, getting there faster, having fun, helping the environment, saving money are some of the main ones. That is why, when the facilities are built, there are plenty of people who will use them.
Further reading: