Commoditizing apps and tightly controlling the market for apps on iPhones benefits Apple, and many of its users, in the short run. But in the long run, an unhealthy software ecosystem can’t be good for Apple, for its users, or for the developers who write apps for Apple’s platforms.
Apple obviously doesn't need to do anything right now. They're making a lot of money selling iPhones. But their store is flawed. It inhibits a lot of applications and prevents talented developers from being able to make a living selling apps. It may not be hurting now, but it will at some point. The point is Apple could do more to make building great apps a viable business venture, and doing so would directly benefit Apple.