Because Apple is the "Gatekeeper" of all software on the platform. They have full control over what goes in the app store, and what doesn't. No longer will you be able to go to a website and download some no-name-joe's software. It HAS to be on the app store. That's the direction it's going in. It has nothing to do with the cloud, being able to redownload your software, view source code, etc... It's about having the choice of what software you can and can't use being controlled by them.