[zaarn]

You don't need it but it's useful.

Normal convective cooling (think your computers CPU or your phone's backside) or evaporative cooling (sweat on your skin, discardable heatsinks) work by transferring heat to some medium. In case of CPUs you do it twice, once from CPU to metal and then from metal to Air to get a larger cooling surface.

In space you don't get that, or atleast not without having it be expensive af. The only way to loose heat energy is by radiating it away naturally (infrared light that our bodies like to emit carries heat away from our body).

This is very slow and requires a very different cooler design and some design metrics overall (if your CPU points it's heat surface at some other components of the craft, that component might overheat due to that).