Because subspace communications are cut off between Bajor and Earth? Picard is totally clueless there is a human slave camp in the alpha quadrant called Terok Nor? That's a weak plot point.
Its more likely the Mirror universe for the Kelvin verse, why the writers won't admit it I don't know. Saying its the Prime Mirror universe does not add up.
They're isolated, why would they have a connection to Bajor? the KCA is probably blockading the system as best as possible, blocking communications and all that.