That's the million dollar question.

[So much remains uncovered about Luceti, so many truths that even he has yet to find.]

The word we're told is that they're trying to find some way to send us home, believe it or not. They- the Malnosso, the ones responsible for the experiments- aren't technically responsible for bringing us here, you see, but they haven't offered any good explanation as to why we're dragged here in the first place. Or why certain people are brought here rather than others.