That's because they really aren't, for these reasons:
1. Genres follow trends. A rising tide lifts all boats, and vice versa. The flagship brand succeeding creates knockoffs, and when it sinks, it takes down the industry. It's held true even for things as dependent on fan-created material as tabletop games. When major tabletop games were crumbling under the weight of brand mismanagement and shitty rules, you
could just make good rules and say, "hey, you can play D&D with this! you can play Vampire with that!" Neither game ever needed the serial numbers. And yet it never happened commercially.
(The only "exception" is Paizo, who, due to some horrifying mismanagement and corruption at WotC, became the sole designated producer of official D&D content. The chance of this happening to Star Wars is about as high as Chris succeeding both Satomi and Ishihara.)
2. As much as nerds like to pretend they're above such faggy things as plot and characters,
they hold together the franchise, not galactic empires and rebellions. Alec Guinness' quiet dignity, Harrison Ford's bravado, Carrie Fisher's huge buns. Factions only matter as they relate to the characters. That fragment of a fan film whose creators got ratfucked the other month (
TURN ON ADBLOCK) was so powerful because it made use of existing characters and the viewers' knowledge of them. Vader, Palpatine, even Padme from the godawful prequels, through her relation to Vader. They were piggybacking off the work of the original trilogy's cast, crew, writing, design, special effects and direction. You'd need all that, but the characters are still of utmost importance. You can have the best visual bible on the planet, but if your lead is a discount Spider-Man who has trouble pretending to be interested in a woman,
it's a nonstarter.
(2a. Self-sustaining interest in spergy "lore" like ships and weapons is pure economy of scale and only kicks in at the scale of Star Wars.)
3. It's product identity, the copyrightable elements, that bring in investors. Without that, you can at most play a Handsome Smuggler or Bounty Hunter at children's birthday parties. Even fan creators need fan masses to rise from and to consume fan works, and fans are made with advertising money. Without a steady influx of preteen boys and that more intelligent sort of girls who like boys' games and books, there are no fans, no fandom, and no fan content.