I get the risk here. But it has to be balanced against the downside of the OS being able to say: "Oh, you'd like to change the default file handler for X? Sure,

I get the risk here. But it has to be balanced against the downside of the OS being able to say: "Oh, you'd like to change the default file handler for X? Sure, just follow this 7-step process to make that happen." If applications can't change this, then an OS with a competing application can just implement a high-friction process that discourages most people from completing the switch.