Thanks everyone for the comments! I should have clarified:

1. I am talking about the no-annual-fee Citi card (mileup card).

2. What I meant to ask was whether there any hidden/less known benefits when booking or flying AA that might make it worth keeping the card, as opposed to having a Citi Rewards + or Double Cash that earn cash or more flexible reward points. For example, for United, they don't really tell you online that even the free United card gives you special access to lower award flight rates you can't get without a United card. However it seems like this is probably not the case for AA. So I think my question is well answered, thanks for everyone's help!