I can see your point - but it’s always about trade-offs for stuff like this, and the cheat is really about quality of light and achieving efficient use of the light rays in the CG world rather than appearance of the light (which, often enough, we don’t want to see at all anyway). The trade-off for visibility is a smaller concern IMO, mainly because it’s much easier and computationally cheaper to workaround, no? I’m not sure of the exact circumstances you are looking at though