I have never seen the real justification for this. I DO follow the clear & obvious rule that lights should be on whenever it's raining & wipers are running... and for 30 minutes before sundown. I use my lights to do something that requires extra light... not to 'make my car more visible'... if it is bright daylight, my care IS visible.

I suspect this is one of those "well.. it 'might' be something good, so let's do it.." ideas. Having lights on in daylight is for funerals and for emergency signaling...etc. If everyone does it, what is left for special circumstances.... turning them off?