@kintux I don't have to enlight you, it's a personal opinion, you may have yours, and I have mine
But one reason is what B.Y.O.B. said.
Another reason is that we may want to play with the light and start the shot from pitch black situation.
Yes, we could have a super tiny light, but why have such a small value when you may want just to turn off the light, or go from 0 and forget about the actual value and having you to animate at 0.0001 instead of 0.
In the end the thing is to make it transparent to the user, but if I have a scene with 0 lights, I want to get 0 light in the render, not default lighting
