Have you noticed a lot more cyclists using their bike lights during the days recently? I have. Actually, I'm not sure if I even noticed this happening at all last year. A day doesn't go by where I don't notice a cyclist using their lights regardless of the time of day.... and it makes sense. These lights don't have to be super bright as you are not using them to see but be seen, a simple blink option light that can be picked up at a bike store for around $20 bucks can go a long ways in protecting you on the road.
All types of cyclists are using them
All types of cyclists are using them from what I've noticed, the Mad Max commuter, afternoon fitness rider, daily commuter and carbon/spandex racer.
It's cheap insurance
Much like a helmet, it's protection that probably will never be needed but if it is needed the savings of having it are immeasurable. Like a helmet, in my 20+ years of active cycling I only needed mine once but it really saved me so like wise I bet using lights might be the same way, rarely needed but lifesaver when noticed. You don't need any fancy lighting system, $20 should be plenty of light to be seen during the day.
Why some use daytime lights
While riding the Golden Gran Fondo I rode along side a cyclist using a light during the ride so I ask, why does he do it, his response was morbid. He said the pedals on his bike was from a dead guy, one of the cyclists killed in a car vs. bike incident in Fort Collins and ever since he got the pedals (from a friend of a friend) he now uses lights whenever he rides, period.
Why not use your lights? Hopefully you own them anyway and only get used a few times during the year, maybe during a cruiser ride or those early fall evenings when it gets dark early but is still warm-ish. It's not like we will go broke buying batteries and if so than just buy one less coffee a week.