Army ants are mostly nomadic and only create temporary nests in resource rich zones.
They send troops to raid the area and when the resources are depleted they move on.

Do you think it would make sense for an advanced civilization to settle in interstellar space and operate in a similair way?
What if they only sent drones to raid nearby solar systems but stayed hidden in interstellar space?
Also chilling in interstellar space means that you are less likely to be struck by planetbusting weapons like an RKV.

Maybe thats why we can't find evidence of intelligent life.
Everyone just realised that moving out of a Solar system is safer.