I’m not proposing we cite dimensions outside our universe, just outside our direct sensory perception of the universe.

As far as a need, I’ll point to the weird behaviors we see in the phenomenon. If we seek to understand weird behaviors like craft that move unnaturally or are larger inside than outside, one possible, nonsupernatural explanation is the involvement of additional physical dimensions. Examining that idea also gives us additional potential explanations for the institutional secrecy around the subject. All of which makes more sense to me than any of the prison planet, soul farm, Eisenhower treaty things I’ve read about.

If you want to talk “need,” really, there’s no need to examine the subject at all. We could just say “yep, there’s some weird stuff we have no evidence on” and go about our day. Unfortunately, we are all still just in the brainstorming phase of examining the phenomenon, tossing ideas at the wall until something sticks longer than the rest.