Often in science fiction, we see aliens enslaving humans for one reason or another. This is a trope I'm attempting to repurpose, but before I go any farther, I'd like to ask: what possible motive or means could aliens actually have for enslaving humans, particularly enslaving humans and taking them to labor on other planets?
I've been using historical examples of New World slavery as a model, but I'm curious as to whether or not this is realistic. Surely the contact between Europeans and the North and South American peoples would have felt "alien," as would have the great differences in technology, but I'm wondering if, given the vastness of space, it would actually be economic or even conceivable in the first place for aliens to do to humans what the European explorers and conquistadors did to Americans.
It's important to me that I find a way to realistically portray such a scenario or to not portray it at all if, in fact, it's not realistic, even though it's been done many times before.
I know it's a broad question, so I'll summarize: would there actually be any economic incentive and technological means for aliens to enslave humans, or would the vastness of space and drastic differences between our species dissuade them from it?