Why SharePoint team starting make a internal functionality without public APIs?

I notice in SharePoint 2013 that the SP team start to change the SharePoint API form very open to somehow closed.

as example: there is know API to add users to Community sites as members (they use internal class and method on there web-parts).

another example: there is no documentation for CSR technology, but they (SP team) use it as framework for default SharePoint functionality.

is there any information why they do that? is there plan to make SharePoint a close product (e.g. livelink)?