but basic keyboards don't use ICs, or?
What makes you come to that conclusion?
Modern keyboards use USB, in order to communicate with a PC over USB some protocol has to followed. Implementing this protocol without using any IC would make for a very large and expensive and power hungry keyboard.
When the keyboard is communicating with the PC it sends codes. Also making these codes without ICs is theoretically possible but your keyboard would require a humming box next to it similar in size to a refrigerator, it would consume a lot of power and it would be expensive.
In an IC we can integrate all the functions above for a few $$ or less.
I challenge you to find a computer keyboard that does not have any IC inside. My bet: you will be unable to find one.