Well I have been riding my bike for 20 years, and not only to school, so go figure. If you have a seperate cycling path, there aren´t any downhills and the commute is under 20 minutes, the risk isn´t so high, doesn´t mean it´s wise not to wear a helmet. If I commute (not often) I don´t take the helmet as well, but at least I know I am an idiot, and can die as a result. Always bring the helmet for actual rides tho, I am not THAT big of an idiot.
I don´t know about what rules are you talking about, if you mean helmet, that´s not mandatory, if you mean vehicles, yes people are idiots, but that can happen elsewhere as well.