Why do aerobatic planes have symmetrical wings?
One goal for most aerobatic planes is neutral pitch stability, which eliminates any pitch response related to air speed, which allows for clean straight lines during dives or climbs without requiring elevator adjustment for speed.

Cambered airfoils produce a pitch down torque which increases with speed, and this would interfere with the goal of neutral pitch stability. This would be another reason for using symmetrical airfoils on aerobatic aircraft.