Experience. This isn't my first time being kidnapped to a world between worlds and time-lines by the whims of someone.

It makes sense anyway, don't you think? As far as we know we're the firsts, but that doesn't mean we're going to be the only ones. Whatever they did worked once, and greatly, but what if that wasn't enough for them? Or what if it didn't work as they really planned? In both cases more attempts would be done. No matter how you look at it, it's more probable that more people will be pulled into this than the opposite.