What makes you think it is a rare phenomenon to them, or that they have the same conceptualizations of "needs and wants" as we do? What if they view these events the same way we view watching paint dry or grass grow? Just as we have to be careful not to anthropomorphize animals and other species, we must also not fall into the trap of anthropomorphizing alien species until there's an actual encounter and we get to 'know' them, once again, assuming their concept of 'knowing' even remotely resembles ours.
For as far as we know, they've observed us, and have long moved on, finding us entirely uninteresting, which seems to be the one explanation we love to overlook, but given we are humans with big egos, love to make ourselves out to be more important than we actually are.