Mass has a lot to do with light. Mass is inertia. If light had mass it would have been able to be stationary relative to an inertial reference frame. Because it has not got mass it always move with light speed relative to an inertial reference frame. A vehicle (with mass) moving with a speed v is stationary within the inertial reference frame moving with it. For this reason the light from its headlights will still move with the speed of light away from the vehicle. Galileo's statement of relativity, subsequently incorporated into Newton's first law, implies that any body with mass has an inertial reference frame within which it is stationary (i.e. both its position and momentum are known at the same time). Heisenberg did not appreciate this scientific fact and interpreted his uncertainty relationship, involving position and momentum, incorrectly. This has led to the farce called the Copenhagen interpretation of quantum mechanics, and to the quaqmire called quantum field theory.
