Picture this: the USS Enterprise coming upon another Federation vessel and not recognizing it because it is flying "upside down."
And why not? For in space there are no directions. A ship might very well confront Enterprise "flying" at 90 degrees to the Enterpise's plane, or upside down, or sideways to it. Our galaxy's stars are not on a single 2D plane (though to be fair, in the old generation there is one episode that I remember where some web spinning aliens flew at all different angles to trap the Enterprise).
If we have similar perceptions about things it is usually related to our natural environment: Enterprise always flies on a flat plane because we are used being pulled in one direction, on what appears to be a flat plane. It makes more sense to our brains that the Enterprise only moves in this way. The perhaps writers never want to throw us off, or perhaps never thought of it themselves.
There is a similar convention with maps and globes, north is our orientation because our compass needle pointed north (Though perhaps it is different with old Chinese maps? Their compass needles pointed south). How often have you seen a map of the world upside down?
This even carries over to how we look around ourselves: we almost never look up. We never need too. Except perhaps for people who grow up, live and hunt in forests where looking up is necessary to survival.
Obviously there are many things that we do see differently, otherwise we wouldn't be such a fractured society. But how much of what you see is colored by your hand-me-down perspectives? your family's? your religion's? your county's? your race's?
The challenge is to see past one's perceptions; to ask yourself: why DO I think that way?