For me, having driven trucks for years, I prefer to be able to turn the headlights on/off when being passed by trucks as a signal that they're clear to move back into my lane. Not being able to easily see the headlight switch in the dark makes it slightly more difficult...and I usually just flash my high beams instead. (something that's illegal in many states) Sure...I could just let the other driver figure it out on his own...but it's a simple courtesy that has been ingrained into me...I do it in passenger vehicles, I've always done it in RV's as well as trucks and cranes.