Others will jump on you (and me ) for saying this but I at least agree. There was just simply no where for another port to go in the design that included a removable battery. Building the battery in, with the lesser constraints on the particular housing and even the shape, made room I think for other features, in this case, the FW800 port and the SD card slot.
I think that the SD card slot will prove prescient, typical Apple.
All the best.