Baseball is one game, but within the sport there exists two different rules for certain teams. The NFL has two conferences, and can you imagine a rule existing that the quarterbacks in the NFC have to throw with their left hand only? The NBA has two conferences as well and
imagine the Western Conference teams don't incorporate a 3-point line? That's the case in baseball; two sets of rules for one game. When you imagine kids on the sandlot picking icons to emulate, it's crushing to picture them arguing over who gets to be David Ortiz because whoever does has to sit on the bench because Ortiz is a DH.