On Earth, the cardinal directions are straightforward. The arrow on a compass points to the nearest magnetic pole. You can then use it to travel anywhere on Earth.
In space, the idea of anything being “central” enough to be used as a “North” (since the universe has no center) or being fixated enough to not somehow pose issues is more convoluted.
If you were a pioneer of space exploration, what would your “North” be?
For the same reason GMT became the standard: Somebody has to make the clocks. Space is pretty big, but if I had to bet money, I would wager that the first intergalactic travelers would start here, where the people are, and they would start with here as their point of reference.
Why would you assume humans are the first intergalactic travelers? The universe is 14 billion years old.