There are... multiple answers to your first question, but the second one is easy, in that I don't know. I've wondered that, too. I tested this out with someone once, but there's a -- barrier. So opening a Corridor doesn't work except for moving around on this world.

[Riku shifts in his seat a little, leaned forward as to not squash his wings. He's sitting on one foot, and the other reaches out as his dog passes. When his toe comes into contact with Shiro's side, he instantly flops next to his master, tail wagging as Riku rubs his belly.]

As for the first one... there are a lot of different reasons. The official one, as told by the government, is what they told you when you arrived, about the war, and about being heroes, and all that. But they -- the way we arrive is uncontrolled. If it were, they'd be able to weed out problems before they arrived. So something else is going on, beyond that. I haven't really... figured it all out, yet. You'd think I would have, considering how long I've been around.