Originally Posted by markbarendt
Well, because light sources aren't infinitely "Intense".
It might be easier to understand by starting at the light source, which has a given intensity which is the high limit (not infinity), and then doing the math as you move away from the source.
Good point. Another way of stating this idea is that at zero distance, the light intensity would not be infinite, but at MAXIMUM, and depend on the FINITE intensity of the light source.