They could choose what they do with the OS and apps offered on it until they created a free marketplace which is bound by similar rules to other markets of products and services. This is what the App Store is considered now. Want complete control over your marketplace whereby you make all of the rules and choices made by those who use your market, then don't open it up to third-parties.
As a third-party, you know full well what the rules and regulations are when you get into business with a service provider. Don't like the rules? Don't get into that business, it's pretty simple. There are plenty of other platforms to develop for.