For the save() operation to be cascaded, you need to enable CascadeType.SAVE_UPDATE, using the proprietary Hibernate Cascade annotation, since save() is not a standard JPA operation. Or you need to use the persist() method, and not the save() method.
From the community documentation:
hibernate.hbm2ddl.auto Automatically validates or exports schema DDL to the database when the SessionFactory is created. With create-drop, the database schema will be dropped when the SessionFactory is closed explicitly.
e.g. validate | update | create | create-drop
So the list of possible options are,
validate: validate the schema, makes no changes to the database.
update: update the schema.
create: creates the schema, destroying previous data.
create-drop: drop the schema at the end of the session.