Why did so few PS2 games support the second memory card slot?

ps2 slot   Dan ps2 slot

ps2 port of my motherboard I've tried another ps2 keyboard and it's working, and my keyboard plus the dim5ps2 cable are working

The Hard Drive goes inside the bay and the network adaptermodem covers it The modem adds some meat to the back of the PS2 beyond just PS2 port and also a VGA port, there is also a

slot demo pragmatic anti lag What is PS2? The PS2 port is a 6-pin mini-DIN connector used for connecting some keyboards and mice to a PC compatible computer system  General Information Category, Keyboard extension cables Description, 6 Pin MiniDIN PS2 Mouse Slot Plate Bracket - PS2 panel