The evidence is implied; it's not a mining/exploration vessel simply because it cloned an army of humans to cleanse the planet.
The whole morning communication with the fake sally also implies the AI is insanely smart; it's a self-sustained, self-sufficient devourer of worlds, gathering resources for anyone but itself would be the actual retarded thing because it would just use them flying back to wherever beyond the solar system it came from. It feeds and moves on.

Heck the TET was lined with drones, but vick stated many times they had trouble getting new materials, which again implies that losing a drone and replacing it with a new one was too costly. So if the AI doesn't want to waste resources on drones, why would it waste them to fly back to its (non-existant) alien overlords?

The radiation zones would also not become "irrelevant", because to the other jacks all those other "humans" are simply scavs/aliens.
Vick has shown she will resist everytime Jack tries to resist, so there's another conflict.
And he both 52/49 have only shown to resist/remember when they were exposed to julia.

And another point, "2 weeks left", I'm pretty sure there aren't actually hundreds of jacks walking around, they most prolly have a soft expiration date after which they are returned to the TET and a new team is formed; "are you an effective team?".
The radiation zones are probably only used to keep new teams away from old teams, I wouldn't be surprised if 52 and 49 were the only ones close to each other.

So with the drones shutting down, which is bs because they have shown to be autonomous and have their own powersupplies, everything else would shut down as well, so no spaceships for the others to use to even get down from the towers.
And even if they were to get down and explore, they had no reason to "look for julia", because they weren't exposed to her; it even took 52 three years to find her.