Other than validation, I can imagine several good reasons why one might want to ...

Other than validation, I can imagine several good reasons why one might want to wrap a primitive inside a class.

For example, you may have a function:

    group_by_age() -> Dict[int, List[str]]

which might be perfectly good for your use case, but I can see why one might instead prefer:

    group_by_age() -> Dict[Age, List[CustomerId]]

for self-documentation and expressiveness.

Your test assertions may also become easier to read:

    assert group_by_age() == {
        Age(23): [
            CustomerId("0471"),
            CustomerId("3390"),
        ],
        Age(42): [
            CustomerId("2334"),
        ],
    }