It’s more so for spotting the trailer in the desert and/or keeping critters from going underneath.
Lights under the trailer will not keep critters away. In fact, it might attract them.
As far as seeing your camper in the desert at night, if you are NOT surrounded by artificial light, your eyes are actually very sensitive after dark. In darkness, the moon and the stars light up the ground so much, you can see for miles. In an area with no artificial light, your camper will stand out like a soar thumb being a geometric shape that is not natural to the surrounding environment.
But, turn on one light anywhere, and your night vision is completely blinded. You can't see anything but that one light.
I am so thankful we live in the country where it's dark and the surrounding lights across the fields are the only lights around. At night, it's awesome looking across the fields, even in the dark I can see the coyotes running across the fields.
For most of 2024 we've been parked at the Audubon State Historic Site near St. Francisville, Louisiana. We are the only camper on the Plantation as I'm a volunteer and this campsite is reserved for a state sponsored Volunteer. Being located away from "everything" and surrounded by thick trees, and no road or traffic or people or lights (except the glow of the security light inside the plantation house) and a street light in the parking lot, it's 100% dark on about 95% of the park property. Night walks with the dogs without a flashlight is unbelievably awesome! Any sliver of a moon and the place lights up like daylight!
So, if you REALLY want to see things in the dark, keep the artificial lights away and use your own night vision. I think you'll be amazed at your own human ability. But ... finding a true dark place is very rare. That's why I love the park I'm at right now.
If you are alone in the desert, then you should know what I'm talking about.