Technically on the low-level, your serialized object will also end up as a stream of bytes on your cable or your filesystem…
So you can also think of it as a standardized and already available way of converting your objects to a stream of bytes. Storing/transferring object is a very common requirement, and it has less or little meaning to reinvent this wheel in every application.
As other have mentioned, you also know that this object->stream_of_bytes implementation is quite robust, tested, and generally architecture-independent.
This does not mean it is the only acceptable way to save or transfer an object: in some cases, you’ll have to implement your own methods, for example to avoid saving unnecessary/private members (for example for security or performance reasons). But if you are in a simple case, you can make your life easier by using the serialization/deserialization of your framework, language or VM instead of having to implement it by yourself.
Hope this helps.