The main reason for insisting on headlights rather than sidelights isn't so that you can see better, it's so that other drivers can see you.
This is especially relevant for drivers of trucks and buses, whose mirrors are on the outside of their vehicle, normally right at the front, above the front wheels. This means that any spray, salt, mud and other road dirt gets flung up onto them. We do have heaters that dry them, but that just dries the dirt on. You can reach the ones nearest you with a cloth, but not the passenger siide ones.
Do you feel safe overtaking, or being overtaken by, somebody who, through no fault of his own, can't necessarily see your car. Turn them on, it's safer.
Happy motoring
Cheers