a lot of the reason has to do with simultaneous arrivals. I believe, by regulation, that runways have to be 4300 feet apart to allow simultaneous arrivals, where planes can be within a mile and a half from each other on arrival. the outside runways 25L and 24R meet this requirement while the inside runways do not. so typically you will see arrivals on the outside runways and departures on the inside runways. Unfortunately that means the arriving planes need to cross the inside departing runways to get to their gate.