An interesting observation...
My boat is under 7m and my motor pushes it at maybe 5 kts, so I can use an all around while motoring unless under state jurisdiction. Then if I use the sails or scull to move silently I can just use a flashlight as needed, but if I crank up the motor, which provides an audible cue that I am moving about, I have to have proper nav lights. I think the narrow part of the Pamlico, which is fast becoming my favorite haunt, is subject to state regs. I was planning to get lights anyway, but its an interesting note.
Newport 17 - "Kohanna"
At sea Darwin's hypotheses is the final arbiter of right of way.