This is a common mis-conception. Among the most common causes of crashes when riding at night are cars coming from the front. Most riders go to good length to be seen from the rear, but are more casual about front visibility. Then they're exposed to cars making left turns in front of them, or entering intersections from the side because they don't see an oncoming cyclist.

Add to that the increased risk of being doored when riding in the city. Even a conscientious driver won't see you if you're coming up unlit from your front.

The reality is that the reflectors help with left turners, but not with entering traffic or people opening doors because those don't have lights pointing toward you to light up the reflector, so regardless of whether there's enough ambient light for you to see the road, you need to have a light in addition to reflectors to ensure you're seen from the front.