They're all over the place back home, it's just that most people don't know they're there.
Let me see if I can explain.
My home universe is sort of a pocket dimension to theirs, as in, I can go to their side of things and walk from Louisana to Moscow in about ten minutes, maybe. Things here take up less space there, if that makes any sense.
They cross back and forth because they feed off all the stuff we generate, emotional and electrical impulses, all of that stuff, it's a wholly symbiotic relationship, because without them there to feed off the excess, it would build up and crack our minds. With me so far?