In specific universes, this is usually explained rather well in universe. But, what I'm looking for here is a more out of universe explanation. Where did the idea of a galactic barrier come from and why have other works adopted it?
To be clear, it's pretty obvious that inter galaxy travel is generally unfeasible even in sci fi, but I want to know why many works make it downright impossible with an actual barrier that seems pointless.
Edit: For those requesting a definition of barrier. The barrier would be some kind of region or existence that literally makes travel impossible or near impossible. It doesn't have to be physical or completely prevent access, but it does have to make the ridiculous concept of inter-galaxy travel even more impossible.
Examples Most of these are taken from the TV Tropes list
- The Star Pit ~
only people with a specific set of psychological issues can handle going outside the galaxy
- The Last Legionary ~
extended stays in Overlight drive humans insane, making it impossible to have a functioning crew at the other end of the trip
- The Culture ~
the Grid — the barrier between this universe the other ultraverses/infraverses ships use to travel— changes properties in extra-galactic space, making ships travel slower.
- Star Trek ~ As explained in the link