1) They make hardly any money from their 30 percent.
2) Why is it obvious that everybody would suddenly switch to not selling through the App Store?
I don’t think alternate app stores on Android are terribly successful. Maybe they are, I don’t know, but I haven’t heard about it. People stick to the defaults and what’s convenient and easily discoverable.
Such a switch would be relevant for very few people. There is no reason Apple couldn’t do it. It just wouldn’t be good or bad for them. They can be lazy.
Here is the relevant quote from Apple’s CFO Peter Oppenheimer, made during one of Apple’s quarterly conference calls: “Regarding the App Store and the iTunes stores, we are running those a bit over break even and that hasn’t changed.”
This is by now an old quote (from January 2010 – how time runs) so things might have changed. There just isn’t any more current information. Nevertheless, if you look at Apple’s numbers it’s pretty obvious that they make the vast majority of their money by selling hardware. Music, videos and apps make the hardware more attractive, not a lot of money for Apple.
With this model Apple misses out on their 30% cut of app sales.