Memes

Depending on the context, it could just be who's doing it. Star Wars was originally specifically an allegory for the Vietnam War, which was a war of Western imperialism because the two countries making it a war rather than a country gaining its independence were France (who'd conquered Vietnam as part of their empire and weren't happy that the Vietnamese didn't want to be in their empire) and the US (who wanted to stop communists gaining power anywhere), both of which are Western countries. It was about that war in particular rather than imperialism in general because that war in particular was the one that was a big deal for the target audience at the time - if Lucas had been Japanese and making the film decades earlier, maybe he'd have made it an allegory for something else, but he wasn't, so he made the film he made.