The airline is required under its pilot deal to have 85% of its regional flying in and out of hubs (defined as the legacy American Airlines hubs, plus airports where they operate 100 or more flights). Austin isn’t a 100-plus flight city. American runs a peak of 78 flights (low 50s on Saturdays, 60s on Tuesday and Wednesday). They don’t have the gate space for more than that, and even if they did that would likely mean more losses. So Austin regional flying to non-hub cities falls under the pilot contract 15% of total regional flying cap.
American isn’t allowed to build an operation which doesn’t support mainline pilot union jobs, and given passenger demand and gate limitations in Austin that means they aren’t allowed to build an Austin focus city as they’ve been doing.