Hi!
Apart from the use case described by Peter, I want to add the following:
As far as I understand it, the point with the scheme described in your quote (Asit) will be useful if the amount of data to be encrypted is large, for instance an attachement to a
SOAP message. This way you can use symmetric key cryptography to encrypt the bulk of the data and then use public key cryptography to encrypt the symmetric key, which probably is considerably smaller than the data.
Also, the symmetric key can be changed with each message, since it will be enclosed in the message.
Best wishes!