There is not reason for you to use streams. Is that detailed enough?
Streams is a change-data-capture system for replication. You are using RAC to protect against machine failures on your primary system. If a large enough problem happens, you can switch over to your standby system. You have no need for replication, so no need for streams.
Note. If you did need some form or replication, Oracle now prefer you to pay for GoldenGate, rather than use streams for free.