There's a theory that these spaceships are possibly Alien AI drones sent here to scan our part of the galaxy for signs of life so when the civilisation who sent these drones exhaust the resources of their solar system, they'll come here, wipe out the dumb humans and colonise the earth. They're probably just analysing our capabilities so when the mothership arrives, they'll be well prepared to annihilate Earth's defenses.
These drones ate probably self replicating(the replicator could be bear an asteroid belt), so there's probably trillions of these things around our galaxy, fishing for precious resources and analysing potential threats.
Again....if they have the means to travel here, what could we possibly offer them?
Any resources that exist on Earth exist elsewhere in the galaxy....and in most cases in far larger amounts than on Earth. So the idea that aliens traveled potentially thousands of light years to jack....I don't even know, water, fossil fuels,
whatever....is ridiculous. And, no offense, that "we are important, the aliens want something from us!" mind state is typical of humans.
If aliens exist, we are not important enough to steal from. If they do exist, them occasionally visiting Earth is probably the space equivalent of slowing down to watch a car wreck. I mean...."analyze our capabilities?"
If they have the tech to come here, they don't need to analyze anything. It would be like us analyzing whether or not a nuke can kill a toddler.
Fred.