People are already upset that their digital purchases are controlled by Apple. Wait until the startup that they bought stacks of software from goes bust and all of their app purchases are gone.
This current situation already exists with the App Store. There are apps that have been removed from the store that are simply gone forever, such as Flappy Bird, which was at least free. So how does this change anything? Just because Apple will outlive third party stores doesn't mean the situation you're describing doesn't already happen.
People are already upset that their digital purchases are controlled by Apple. Wait until the startup that they bought stacks of software from goes bust and all of their app purchases are gone.