Got to love laws, their interpretation, and their enforcement.
If you've ever pulled a flatbed car trailer that is over 80 inches wide, as most of them are, TECHNICALLY you were required to have these cab lights. Yep. For hire commercially or just some Joe hauling air, across town or across the country. 80 inches wide or more is the key.
Clearance lights are the single red or amber lights placed on the furthest outside edge of either side of the vehicle. You see these on dually 1-ton truck fenders. The triple, center mounted red or amber lights are called ID or identification lights. They, as the name implies, identify the vehicle as being 80 inches wide or more. Tractor + trailer(s) = vehicle.
Any vehicle over 80 inches wide are required to have this lighting - ID and clearance, the set of 5. My double jet ski trailer is 84 inches wide, fender to fender. On it I have the 3 red rear-facing ID lights & each fender has red and amber clearance lights. To be "legal" while towing it, the towing vehicle would be required to have front facing triple amber ID lights. Which I do not have, yet I am over 80 inches wide while towing it.
I'd say these cab lights do not imply a vehicle over 80 inches wide, but suggests potentially over 80" with a trailer. Either way, you've got to be doing something really stupid to attract DOT & law enforcement attention to get stopped on having (or not having) these lights.