Why you should wear a cycle helmet
- They ought to prevent cuts, scrapes and bruises to the top part of your head, and mild concussion (feeling a bit woozy), in the event of coming off your bike. Such things won't kill you but could ruin your whole afternoon. One of the original purposes was off-road cycling where hitting your head on low branches and stones next to the track then became a preventable danger. 
- If not wearing a helmet makes you feel sufficiently at risk to avoid cycling at all.
- If your mates are calling you names for wearing a helmet then you could continue to do so as practice in not being told what to do.
- Some insurance companies sometimes claim a cyclist has contributed negligently to "accidents" they're involved in by not wearing a helmet, even when there has been no head injury. In fact, no such claim has succeeded, partly thanks to CTC lawyers .
- It's a good place to put a rear light since it's the highest point available. Also you can get neat helmet-mounted mirrors.
- Some organised events and venues, and countries, and partners, require them.