Apple is blurring the lines between software and SAAS.
I expect to pay a one time purchase price for an mobile application that has no additional maintenance besides support for OS upgrades. The developer is going to make those anyway to continue selling their app on my chosen platform. There's no reason I should have to pay just to keep the lights on. Patches should also be included. I paid for a working app, not a bundle of bugs. If you're going to add a bundle of new features and sell it as a "pro" version of the app, or whatever, I'll give it a look, but I may be perfectly happy with my original purchase and have no desire to "upgrade". I'll keep using the one I bought until you stop supporting it, and then I'll delete it an find a replacement that may or may not be your product.
SAAS is a different story. Say I install an app like MLB At Bat. There is an annual subscription for content (similar to buying a season of NFL Sunday Ticket). The app is secondary because what I'm primarily paying for is the content. If the content provider is doing their job then the subscription should cover the cost of the product, product improvements, and patches.
The bottom line is that not all software is a service even though money-grubbing Apple would like to treat it that way.