For Apple it makes sense to make Apple specific alternatives to every software possible. Each one helps to strengthen product value and keep consumers tied to their products.

But it is also a disadvantage of Apple software that it is Apple only. People are cut out from collaborating with others who use other systems. Also Apple aim will be always to provide minimal set of features, to serve the broad user set. They surely won't support software that is not widely used.

All in all while it makes sense to Apple it is distruptive for the whole ecosystem of apps and services. From a developer perspective it makes me wonder if writing any Apple specific software makes any sense at all.