Some trailers will have a second switch wired so that you don't have to (say) climb over the bed to turn the lights off in the morning. Something like that, perhaps?
1995 Airstream Classic 30' Excella 1000
2014 Ram 2500 Crew Cab with Cummins 6.7L Diesel
Sold but not forgotten: 1991 Airstream B190
Sold: 2006 F-250 6.0L Powerstroke Supercab