Actually I think this is a great idea - MSFT isn't saying they won't run their own payment engine, they're giving devs the choice on whether or not to use their payment engine.
This is far superior to Apple's current policy right now.
There are some pretty extreme advantages to tying yourself into the first-party payment engine. As you've brought up, it's way easier to separate me from my money if all I have to do is type in an ID that's already pre-registered to the device. There is in fact a large incentive for devs to go first-party.
But that's not true for all cases, and the edge cases really make iOS a painful platform to use at times. Amazon can't integrate their book store into the Kindle app because Apple wants their cut. As a consumer, I don't mind giving my CC info to Amazon and signing up for their account, and Apple's policy makes my experience as a user noticeably worse.
The incentives for most developers to go with the first-party payment solution is IMO enough - Apple's enforcement here just seems heavy-handed and unnecessary.
This is far superior to Apple's current policy right now.
There are some pretty extreme advantages to tying yourself into the first-party payment engine. As you've brought up, it's way easier to separate me from my money if all I have to do is type in an ID that's already pre-registered to the device. There is in fact a large incentive for devs to go first-party.
But that's not true for all cases, and the edge cases really make iOS a painful platform to use at times. Amazon can't integrate their book store into the Kindle app because Apple wants their cut. As a consumer, I don't mind giving my CC info to Amazon and signing up for their account, and Apple's policy makes my experience as a user noticeably worse.
The incentives for most developers to go with the first-party payment solution is IMO enough - Apple's enforcement here just seems heavy-handed and unnecessary.