The problem is that in our game, the trooper taking a shit isn't the one directing inter-system warfare across the galaxy. The minor characters aren't the ones running factions.
I love to read stories about all types of characters and you can do that regardless of which way you go, but in terms of each of us having control over the factions from a story angle, its usually easier to not do it along side canon. You can do it, but then instead of creating your own characters as the leaders etc, you have to use characters created already. Not impossible, not bad, but you have a wider range of options stepping away from strict canon. You also don't have the responsibility of making the canon characters ring true. I never felt comfortable writing posts with Mothma, Ackbar, Skywalker, etc.
And just to point it out again, if ANH were a video game it would be more like one of the 1st person games in the franchise, not Empire at War, which is closer to what we're doing i think, right?