Why is DFW so great and important? If Dallas Love would be incapable of handling the traffic load without DFW, competition for slots there would drive up prices enough to make DFW worthwhile. But if Dallas Love could handle the traffic, DFW would seem a waste of money.
DFW is a "joint" production of Dallas and Fort Worth. Both cities had to agree to close their airports so there would be sufficient traffic to make the fledgling regional airport viable in the beginning. Fort Worth closed Amon Carter field, and Dallas closed Love Field.
Without the agreement, there would have been no DFW.