Serialization is an alternative way for deep copy.
In Serialization, whole object graph into a persistent store and read whole object graph back when needed. This is exactly what you want when you deep copy an object.
When you implement the deep cloning, the copied object may contain some other object its references are copied recursively in deep copy.
Cyclic dependencies will be a big problem while implementing deep copy. It does implements deep copy implicitly and gracefully handling cyclic dependencies.
Serialization is more expensive than using object.clone().
Not all objects are serializable (transient variable cannot be cloned).