There is something wrong with your searches.... looking at this week, AA has:
- 5 daily ORD-SEA, including a 5pm, 8pm & 10pm
- 3 daily SJC-ORD at 7:45am, 1:25pm and 10:45pm
- 3 daily SJC-ORD at 9:55am, 5:10pm & 8:05pm
- 4 daily ORD-RSW including a 3:10pm
- 10 daily MIA-ORD, including a 9:30pm
As for ATL-ORD & MSP-ORD, the latest departure makes sense as it connects with the last outbound bank at ORD. Non-hub airlines will typically have later departures to other airlines' hub cities.