I am in Southern, California and I have noticed over the last few years that many drivers are driving with their headlights on during the day when weather is clear, bright and very sunny! Not close to dusk/evening hours at all.

I'm not referring to days that are overcast, inclement weather when having the headlight on would make sense during the day.

This is something I never used to see but have noticed it for a few years now that drivers have their headlights on all the time. Not all drivers are doing this but many are (all types of cars.) There is no law in the California Motor Vehicle guide that requires drivers to drive with their headlights on during bright sunny days so it is just the driver's choice to do this of course.

So I was wondering why all of a sudden that people are doing this now, (only in recent years.)?

I could see if there were visual problems like overcast, cloudy days, rainy days (like the weather today.)

I don't see how having the headlights on all the time, is of any advantage "to be seen" under weather that is daylight, bright and sunny which is that way mostly all summer long here. 90 to 100 degree weather on many days and not a cloud in the sky but headlights on many cars.