Or maybe, the model is actually just rather complex and a good API cannot be just a bunch of random methods on some losely related entities.

Or maybe the non-functional aspects of the implementation need to be carefully considered before releasing an API that makes safety, correctness, security, or performance impossible.

Or maybe the developers have an inconsistent specification and delivering piece A now makes it logically impossible to ever deliver piece B, which is arguably more important, but got lower priority because noone took the time to understand the whole thing.