The only reasons we have Sectors now is to force us to employ more Governors. But because the Sectors are set up so retardedly, I get sectors with 5 interesting planets (plus habitats, if I am inclined to build them) and some with one (+habitats, but why bother in a garbage tier sector).
Before you just made 1 or 2 sectors, and had one super effective governor manage it. Also dumb, but on the other spectrum (imagine the stress and the rampant corruption, if the supreme leader can just handle 5-10 Systems, and some random Governor handles ALL THE REST).
The sweet spot probably lies somewhere in between: let us set our sectors ourselves, but if we overburden our governors, they tend to be overworked and develop negative traits (substance abuser, arrested development, stubborn). In fact, administrative cap could be used as a measure on the pressure put on any given governor. Having small and manageable sectors might even reduce the pressure on administrative cap, while having ones that are too big (or completely unmanaged) might improve it.