Safety first
In nature we see many examples of how animals with vulnerable bodies, like snails or turtles have shells to protect them.
Your brain is not only just the most important part of your body, it's also the most vunerable part. Just like snails or turtles your brain needs protection from injury.
Although you may think your skull bone is hard enough, it's not - and can fracture very easily.
You will need extra protection for your brain!
COOL KIDS WEAR LIDS
If you wear a bicycle helmet whenever you ride your push bike it shows that you actually got brains to protect :)
Not 10 years old yet? Then it is very dangerous to ride your bike on the road without having an adult riding along to show and to look out for you.