Use of shared secret "other" than key creation
Shared secrets can also be used for authentication. He who knows the shared secret, is trusted.
For instance, this is used in IoT scenarios, where nodes communicate via DTLS and use the secret as a PSK instead of a certificate and a keypair.

Of course, this only makes sense if the shared secret has been preshared or calculated via some algorithm. The result of an online key agreement like DH cannot be used for that.