It's not that reactors are needed in the permadark regions, it's just they they tend to be very cold and it should be easier to dissipate heat from the reactor.

I think there is reason on mars - there is a fairly significant source of water there (ice). I guess this wouldn’t explain the moon though.

The darker locations are co-located with the largest water ice deposits which are exciting for the possibility of a human presence.

Yes, I specifically mentioned the poles.

It's likely we'll want to go other places eventually, though, and then you're back to reactors, or carting around enough batteries to last you two weeks.