Since games are basically global these days (since the Japanese version must work with the European version and must work with the USA version for online play), its a blanket decision that applies globally.
edit: I'm rate limited, responding here:
I just pointed out that versions don't have to be the same to play online. I remember people complaining that the releases were different, so I'm just asking.
Sure, a dedicated fan can do that. But when you consider the outrage is from typical people (who do not have the technical skill to implement these mods), then it makes more sense.