In town, many people drive with the fog lights on day and night. I assume they misunderstand that fog lights are NOT to be used as driving light. At night, driving on a clear drizzling rain night with fog light on, contributes to road glare. Pain in the rear end. Ed
Let me fix your definitions for you, starting with low beam and high beam lamps. Low beam
: Standard lamp for most driving situations. Beam shaping generally have a sharp cutoff on the left side of the vehicle (for LHD) to avoid glare for oncoming traffic that tapers up towards the right side to allow more lighting on the side of the road for pedestrians, etc.
Low beam isolux (Hella 90mm LED low beam module):
Note the beam reaches a maximum of just under 200m (656 ft) on the right side, but is much more constrained to reduce glare on the left. Also note the "hot spot" in red. This indicates a lot of foreground lighting on the pavement right in front of the vehicle.High beam
: Specialized lamp for long distance illumination. Should be used where there is limited traffic as measures to limit glare are minimal. Also beneficial for higher speeds.
High beam isolux (Hella 90mm LED high beam module):
Note the beam reaches a maximum of just over 300m (984 ft) and all the beam shaping to reduce glare seen in the low beam isolux is gone. Also note there is no hot spot at all. There is minimal foreground lighting and no horizontal cutoff.Fog lamp
: Short range speciality lamp. Short, wide beam with a sharp horizontal cutoff used for foreground lighting.
Fog lamp isolux (Hella Rally 500 fog lamp):
Note maximum distance is 35m (115 ft) and the beam is wide, about 15 to 20 m wider than the low beam isolux. The hot spot is back too, indicating foreground lighting. Should be used with low beam headlamp during inclement weather like rain, fog, sleet, or snow. Can be used by themselves in incredibly severe weather when there is extreme low beam headlamp back-scatter (like a blizzard) if speeds are low enough, 30 MPH or less. Any faster and you're outdriving the lamp. The short range and sharp beam cutoff makes them generally inoffensive to oncoming drivers.
99% of all vehicles sold today with OE auxiliary lighting use a fog lamp. Of those, 90% are completely junk and little more than an additional marker lamp (some actually use a marker lamp bulb!). Per FMVSS, fog lamps on new vehicles automatically turn off when high beams are selected. The Hella 500 shown above is a fantastic fog lamp. OE fog lamps perform far, FAR worse. Driving lamp
: Long range speciality lamp. Long distance beam used for long distance lighting.
Driving lamp pattern (Hella FF1000):
Now we're talking! Maximum distance is out to 475m (1,558 ft) and there is light everywhere. This would be a great supplement to high beams or even as an outright replacement for them. Incredibly offensive to oncoming drivers and generates tons of glare and back-scatter in inclement weather. As a note, the FF1000 is a 7.7" lamp... it's big. Most driving lamps will not have this type of performance, but it illustrates what a driving lamps is perfectly.
Moral of the story... fogs lamps are generally inoffensive and on most OE vehicles, driving lamps are offensive and are typically added aftermarket.
A large percentage of people who purchase aftermarket auxiliary lighting end up with a driving lamp. If you drive around well traveled areas with a driving lamp on all the time, you're a butthead and may as well just turn your high beams on too. If you drive around with a fog lamp on all the time, especially an OE fog lamp, you're not hurting anyone.
Unfortunately, most people don't know or just don't care,. They'll buy whatever cheap auxiliary lighting they think looks cool from eBay or Amazon and drive around as if there's no difference. Even worse are cheap LED light bars. These aren't even driving lamps. They're just flood lamps with nearly no effort toward beam shaping.