Some people don't seem to understand how some programs work.
Let's say a developer spends a *lot* of time making an app for iOS 5. It uses special iOS 5 APIs, system files, etc.
They make the app work really well. They charge $xx for it.
Then iOS 6 comes out. The app suddenly doesn't work. The developer has to go then and figure out what changed between iOS 5 and 6, work on new stuff that both works in iOS 5 and iOS 6, and/or starts a whole new thing that works on iOS 6 (while leaving the iOS 5 version separate).
They may end up spending almost as much time updating for iOS 6 as it did for them to originally create the app in iOS 5.
So what they do? They ask for more money.
HOW DARE THEY! Their time is obviously worthless! I should give them $0! ~My~ time is worth something, so I shouldn't have to give them money!
You think you can do a better job? You spend hundreds/thousands on a phone, but then refuse to give a developer a few bucks to make software for it?
Yeah, so pay 1,99 for exactly the same tweak when iOS 7 comes out, and then the same thing with iOS 8, iOS 9... Ad infinitum. Does it make sense?