That used to be the case, but not any more. The start of interleague play, the elimination of the league presidents, and the elimination of separate umpiring staffs for the two leagues are all moves toward a situation like in football. MLB is analagous to the NFL, and the two leagues are basically the equivalent of the NFC and the AFC. The DH is the only difference that remains, and with the current climate that difference really needs to be eliminated.