Spring Transactions With Supports Propagation

I would like to understand the use of having a spring transaction with Propagation Supports. The java docs mention that if the method which has @Transactional(propagation = Propagation.SUPPORTS) is called from within a transaction it supports the transaction but if no transaction exists, the method is executed non-transactionally.

Isn't this already the behavior of spring transactions irrespective of Propagation.SUPPORTS?

public class ServiceBean {

    @Transactional(propagation = Propagation.SUPPORTS)
    public void methodWithSupportsTx() {
        //perform some database operations
    }
}

public class OtherServiceBean {

    @Transactional(propagation = Propagation.REQUIRED)
    public void methodWithRequiredTx() {
        //perform some database operations
        serviceBean.methodWithSupportsTx();
    }
}

In the above code example, irrespective of whether methodWithSupportsTx() has @Transactional(propagation = Propagation.SUPPORTS) annotation it would be executed in a transaction depending on whether methodWithRequiredTx() has @Transactional annotation, right?

So what's the need/use of having a propagation level SUPPORTS?