Why do most games only use the first memory card slot on the PS2?

PlayStation 2 Memory Card - ps2 memory card slot 1 not working Yeah sometimes one save can just get corrupted like that Did the PS2 shut off mid game or did you use the switch on the back or anything while ps2 memory card slot 1 not working Update to latest version and try loading a game that has saves on your memory card from any version prior to the June 7th version Expected

vulcan slot Note: The MX4SIO card has to be in Slot-2the second MC-slot! Software Steps: 1) Install FreeMCBoot onto your official Magic Gate memory card