If an Alien civilization has the means to visit us, they are beyond the point of needing more resources.
Same reason an Alien spacecraft has never crash landed on Earth - Aliens don't crash the car.
Same reason an Alien spacecraft has never crash landed on Earth - Aliens don't crash the car.
One of the interesting concerns about being an interstellar civilization kind of related to the great ant war that I think was documented in a Kurgesstz video about the relentless expanding invasive army ants around the world.
They used to not attack neighboring colonies because they all shared the same smell. At some point one of the species diverged and had as a different smell and now the unopposed growth of the one species now fights in huge battle between their own species that just smell slightly different.
Likewise, if you have a large distance between two stellar colonies. There's going to be a smell evolution over time.
Humans fight a lot of intraspecies wars but not nearly to the extinctive ferocity that a war between two different species results in.
How long before you send individuals to another star do they consider themselves another species?
I mean look at what happened with Hitler and other genocidal actions.
Isolation due to the communication delay (e.g. ~8 years round-trip in case of Earth to Alpha Cen) and the likely need for adaptation to the new world (be that by means of evolution or genetic engineering) would drive both home world and colonies apart quickly.