Everyone has there own individual "line in the sand" when it comes to safety vs. comfort/style/expense.

Many who smoke cigarettes STILL don't believe smoking causes health problems. Or the joy of drawing nicotine into their lungs outweighs the eventual, probable (but not certain) consequences.

Many who drink alcohol to excess STILL think they can handle driving a motor vehicle. They are willing to take the chance that they will get caught or cause an accident.

Many people have expensive hairstyles that they don't want crushed by a bike helmet. Or they think a helmet is just too geeky looking. Peer pressure can be a factor. And many people just CAN'T STAND something - anything - on their head. They are willing to take their chances. Others are just stubborn.

There you go.