NES/SNES/Genesis etc. Cartridge pins?

[zedrein]

Now this isn't a thread asking for specific pins on the carts for the said consoles, it's more of a general question about what the pins actually do.

I've noticed that all of the cart based gaming systems' carts have multiple pins on them, but considering that a game console is a digital device, why couldn't their cartridges simply have a single pin where all of the binary information travels from to the console itself? Why would the cart need several pins to transfer all of that raw data?

I was actually looking at a .pdf file of the NES cart pinout and it used terms like "PRG A01-A011" for some of the pins, and "NC" "CHR" "IRQ" "EXP" and "NC" for the other pins. You don't have to be specific about all of those terms, but why are so many darned pins for the information in the first place?

Thank you for your time

[kendrick]

Cartridge connectors often serve purposes other than connecting a serial ROM. The Genesis 32x and the Jaguar CD come to mind as interfaces that took advantage of the other bus signals. Also, a single serial connection for memory access is wildly inefficient, so why use it if you don't have to?