Because every Python object also contains a reference count (which needs to be modified whenever the object is passed around), a `const PyObject*` is effectively useless.
This special casing just had not been implemented yet. But as it is an interesting optimization, more so with multi-interpreter or no-GIL Python, the developers will actually introduce immortal objects in Python 3.12 to avoid counting references on some objects (PEP 683 has been accepted):
