Why do Marine vehicles have lights?

[Vermintide]

Y'all also seem to be forgetting that if you get a sufficiently powerful light source and shine it in somebody who's using IR/Thermal, you just blinded them unless they have some automated dimming effect. Thermal likewise is also fairly easy to dupe and hide from compared to the visible spectrum, and you can even manipulate radiation so as to present a different profile to IR cameras. There was some Brit company partnered with Americans a couple years ago developing cells which you could layer on top of vehicles that could dampen/manipulate radiation from a heat source, thus allowing you to make a vehicle look like an SUV or even a cow on IR, or to severely dampen the radiation to make it, not invisible, but quite less obvious (similar to a Polar Bear).

If I wanted a logical reason for SM vehicles to have headlights, this would be it. Blinding enemies and making their IRNV less effective.

 

If I remember correctly there was some kind of operation in WW2 where the Brits hid a column of tanks or artillery (don't remember exactly) from aerial reconnaissance using this principle. Shining a concentrated group of spotlights into the sky meant the vehicles on the ground were invisible through the glare.

 

Besides 40K is a pretty low-tech setting all things considered, or at least it was during the era the original vehicles were designed. True night vision devices probably quite rare in practice, and not always functional. It pays to have a reliable alternative just like every army in this universe still uses swords.

[BLACK BLΠFLY]

Imperial vehicles had spotlights to negate night fighting rules.

[FormelyKnownAsSmashyPants]

Because the miniature designers decided to ad headlights to the vehicle?