Eh? Fantasy has an established canon, kinda regardless. Wispy up-themselves Elves with bows, tank-tops, swirly tattoos and fast daggers, hairy dwarves with axes, hammers and mead, men who are kinda the in-between and yet someone always win or don't loose, and either Orks, Orcs, Goblins, or some other 4th creature that's half noble half warlike to drive the plot. Also dragons, daemons, other demons, zombies and some manner of wench.
Takes all of 1 hour intro for 99% of gamers to be on the page.
Space though...hour on flight, hour on weapons, hour on Alien race 1, hour on 2, hour on 3-5, hour on cosmic deity bullshit, hour on why I should care, etc...
Takes too long.
KOTOR has a roughly 6 hour intro. Skyrim's in 15min.