The constallations are spread for coverage and are in low earth orbits for signal strength, like sharks they have to stay in motion .. and many of the orbits are "precessing" .. they go about the earth and that great circle "ring" itself is turning - physics dictates that they go over all the surface sooner or later.

The SKA proposal is that comms constellation satellites switch themselves off (stop transmitting) when over the S.African and W.Australian SKA exclusion zones.