Taking
@LeeRatters posting as an example...
Those of us who started driving in cars that did not have those driver-aids and automatic systems, or at latest cars with less automatic systems (such as automatic mirrors but not automatic headlights), we would have to do it for ourselves. When there's fog, we turn our lights on. It's something we have to do, that we ended up becoming used to.
Once we moved over from older cars to a more modern car with more technology, some of us just can't get rid of those old habits. If the car have those automatic system, like Daylight Running Lights, that comes on when you start the car, and it just shows front lights but no rear lights, then once there's fog, most of us, out of habit just switch on the headlights to normal dipped beams, which would includes the rear lights.
That's what makes us good drivers, sometimes for us, it's a case of training and drills, you happened to trained yourself to turn on your lights every time there's fog. Rather than relying on the car to do it for you.
It is possible that new drivers who started with the modern cars, are like "Wow! Automatic Daylight Running Lights!" so off they go, then when fog comes, they're either too lazy to turn on the lights to dipped beams (so they would have rear lights on too), because they would assume the car would do it for them.
But that would be mainly due to them being too lazy to read the manual that would have told them this fact, or too full of pride in themselves. It's the same with...
We open a box and take out a brand new camera.
Wife or girlfriend: "Here's the manual."
Us: "Oh puh-leeze! I wipe my bum with manuals!"
@stevewestern It is most likely that most drivers are too lazy to read the manual and realise that the automatic Daylight Running Lights does not apply to the rear lights, so in the even of fog, they're supposed to turn on their lights to dipped beams. That's the first step of the problem, too lazy or uncaring or full of pride to read the manual.
Experienced drivers who started in older cars, are likely to turn on the dipped beams which would include rear lights, mainly out of experience and habit.