Yes, that is convenient. But it's an abstraction you don't always need, but still always pay for.
That's why I would suggest that were possible the kernel should only expose something at most as high level as UDP, and we build the TCP abstractions on top of that in user level. Of course, you wouldn't want to re-write everything from scratch all the time: you'd use libraries.
The nice thing about user level libraries is that you can swap them out for better versions or for different abstractions without any privileged access.
That's why I would suggest that were possible the kernel should only expose something at most as high level as UDP, and we build the TCP abstractions on top of that in user level. Of course, you wouldn't want to re-write everything from scratch all the time: you'd use libraries.
The nice thing about user level libraries is that you can swap them out for better versions or for different abstractions without any privileged access.