The Table Protection protects all DELETIONs. It means the Table Protection feature and the Expire Data setting are not able to exist together.
If table is enabled the Table Protection, the Expire Data setting is not available on it.
If table is set the Expire Data setting, the Table Protection is unavailable for it.
To save the data volume of protected table is not rare situation. To allow the Expire Data for protected table helps such a case.