American Airlines Basic Economy fares are highly restrictive. The purpose of these fares is to make the travel experience worse, in hopes that you will spend more money to avoid them. However they need to balance that with the risk that you will just give up on them and choose to fly someone else instead.
American Airlines President Robert Isom, speaking at the Cowen and Company Global Transportation Conference, admits that “the premise of basic economy, it wasn’t a price cut…[but] an upsell.”