Mmm, maybe it's just because it's a spaceship...? If something nasty happened to part of the ship, they'd need to be able to seal it off...I don't think it would be a problem if we had power.

[Part of the issue is that they don't have the proper access to any of the doors, so Ren is just kind of figuring it's part and parcel of the fact that they're in a giant spaceship that could probably have a number of delightful things go wrong with it.]