That probably comes down to most bicyclists are not trained to ride in traffic. Yellow or bright green/orange safety vests are a must in traffic. I spent five years on a project where I analysed police records on pedestrian and bicycle traffic fatalities, and in nearly every one of these incidents, the driver told police they didn’t see the person. I’d never thought of using lights except when it’s dark or darkening. It’s an excellent idea to have them on at all times in traffic — for the same reason the EU requires cars’ lights to be on.