The iOS development cycle works the way it does to protect Apple's customers. The people that pay for your application deserve and demand a certain level of quality. They also shouldn't be constantly bothered with updating your hastily developed, poorly tested, 'rapidly iterating' product.
As for Android, Google doesn't care. The person with the Android phone is not their customer, they're the product. Google is in the business of delivering users to advertisers. They are just barely in the business of making devices, and that's really just to feed more users to their advertisers by making a product that's as good as the iPhone and also to hedge against a single Android phone manufacturer from owning too much of the total Android market.