Only when I started biking did I realize how much space a bike took vs how much space a car took, how much resources and money was spent for bikes and how much for cars, how much negative externalities bikes cause vs how much cars cause. Many people I know tried to commute by bike but stopped because of how dangerous biking is (due to modern city planning). People like me who are young, single and male are more willing to take risks. So people like me continue to bike and continue to be annoyed by how much resources are given to cars vs bikes. If you want to see a diverse group of bikes, look at the Netherlands. There or is much safer to bike, so you will see more diversity. You'll see bikers who are old and young, male and female (not too many Indians, Chinese, Native Americans, or middle easterns, but that's more for geopolitical reasons).