Alright, I see.
Think of it like this:
An application is responsible for creating an entity, but, for some weird reason, the entity has no identity until it has been persisted in and processed by some third party the application knows nothing about.
This third party might be unresponsive, locked up, under heavy load, or whatever.
The application will just have to sit there and wait to get to know the identity of the object it created itself.
Doesn't this sound awkward?