I realized something: iOS (iPhone, iPad) apps feel different than websites, not because of the form factor, but because of the fact that you can easily pay for them. Apple made micropayments possible for developers, and in turn, that made a new type of app, a new type of content possible, because developers are now being paid for it. Apps don’t depend on pageviews (to serve ads).

It’s the payments, not the form factor that made the explosion of apps possible.