just another wind screen:
you are quite right. perhaps Chicago should have built ORD (orchard field) with the condition that MDW be non air carrier only. this could still be done by declaring the runways to be only 3800 feet long, with the rest as an over-run. not too many air carriers could make money at that field.
so too with the other metro area short fields that have been kept in use even thought JFK, IAD, DTW and the rest have been built.
j