I always chalked it up to needing the light.

That's the primary reason, but I realized I hadn't really addressed the author's argument, which was about thermal design. The problem is not always about getting rid of heat. The problem is about making sure you have the right amount of heat. That means rejecting it when you don't want it, and acquiring it when you do. When you have such a nice solar source of heat available, it's a simple matter of taking as much of it as you want and ignoring the rest.

As I recall, the Voyager spacecraft cooled its electronics by simply letting the heat radiate away through vanes into space. But if things started getting too cold, the vanes would close and simply reflect the heat back into the interior of the spacecraft.

I've seen spacecraft designs where a coolant loop simply takes heat from the sunlit side and radiates it out the shaded side. JRKeller is much more familiar than I am with the particulars and needs of thermal design, so I'll defer to him to elaborate or correct any of this.