After years of being a customer of Capital One I have learned the following: Many things that may be available for your card will not be offered to you proactively. They will wait for you to ask for it and then they will say: "yes sir, that option is available".
I am not saying that they will give you whatever you ask for. They will give it to you only if it is available but never before you ask.
When it comes to Cash Rewards, sometimes your account may have this feature available but not active yet.
Call customer service and ask them if they can activate this for you. If it is possible they will do it for sure..