In most instances, it is the FED DOT who is tightening down on these lights and existing regulations. Most all the DOT checks are setup along major highways, and it is the DOT's privledge to wave you into their checks and unfortunately you must comply with the DOT laws whether you like them or not. Many state DOT are also getting into the game with roadside inspections, my state, New Mexico is one of them. All this adds up to you being legal and also revenue. I will not speculate what their real purpose is, but I am sure SAFETY goes a long way into this picture. Lighting falls under safety.
I drive a 1-ton, the clearance lights came as standard equipment on my truck. In 2006 there were some factory ERRORS and some 1-tons did not have the lights - Chrysler actually had a recall to get them installed on the 1-tons - they are a build requirement to be able to even sell a 1-ton in the US.
I can speculate answers to your questions - the lights come on because it is a law that they do regardless of whether your are towing or not, it TELLS how a truck is equipped with respect to weight capacities, etc. I am old enough (gasp on that admission) and recall a time when cab lights were actually switched seperately in semi trucks, maybe those guys only turned them on when towing wide loads, the cabs them were narrower than those of today.
As far as who has gotten tickets, plenty of people have gotten tickets, there ARE dicussions about tickets on all the truck forums, there are also a lot of discussions about changes in laws that occur every year with respect to towing, etc, you might want to find them and get familiar with them.
I could go on to tell you that the DOT does not care whether YOU find their laws rediculous or not - their laws ARE the law and it's federal laws, you will quickly find that you can't fight city hall and compliance is mandatory to travel on our federally funded roads - and also note, there is not a public road in America that does not have fed funds in them, even gravel roads have a percentage of fed funds.
It is your mode of fuel - DIESEL - that really distinguishes you from other gas 3/4 and 1-ton trucks, combined with your weight class and plate class. Like it or not, we DO have to comply, the manufacturers of our trucks have to comply before they even sell a 1-ton. For years, the Fed DOT's, the StateDOT's, even the State and Local police have looked the other way with regard to a lot of stuff because more and more people became drivers of trucks for non-commercial purposes. I think those days are now over, and there IS a significant push to get everyone compliant with the basic laws.
I was just trying to fore-warn people, not start a debate. My truck IS legal, nothing else for me to consider, I have been waived into a couple DOT checks and passed their scrutiny, no warnings, no tickets,no fines to pay - and most of all I have not been red tagged and forced to park my truck until the problem is fixed and signed off with an evern more scrutinized level of inspection. I have seen people towing loads down the road that exceed their basic drivers license class, and some of them HAVE also been waived into these DOT checks, and their vehicles were parked until someone with the appropriate class of DL was put behind the wheel and legal to proceed. The average DL issued from every state covers people driving a max of 3-axle combination and a tow of less than 10K. Think of it this way - you already drive a vehicle with what is considered 2 axles, how many axles can you legally tow behind the first two?? And as I said earlier, the DOT's and police have basically ignored that basic law associated to your DL, but now, they need revenue, will they continue?? ALL this goes beyond the basis of this thread, but it is food for thought, and good food at that when it comes to your travels.
Again, I was just giving out/stating information that IS applicable.
CD