system
Given the following post, respond as if you're commenting on Reddit:
human
[General] Why do most big sci-fi franchises take place in a single galaxy?

Star Wars. (Discounting Legends) Star Trek. Warhammer. What these have in common is that they take place in one galaxy.

Why only one? Isn't the universe estimated to contain billions of them?
gpt
Because galaxies themselves are *massive*. We haven't even set foot on other planets much less discovered other solar systems in our time. Interstellar travel is an ENORMOUS feat in and of itself. Intergalactic travel would be crazy. You could spend several lifetimes just seeing all that a single galaxy has to offer.