Now you are sharing a transmission line with others and have to follow rules regarding impedance and propagation delays. But you buy these cables with connectors attached. Years ago putting up a text menu on a CRT and waiting while a user typed his choice on the keyboard was enough, but now if your software does not respond asynchronously to any of a hundred mouse clicks, keyboard accelerators, window re-sizes and whatever you don't have a chance of selling your program. No big deal, people learn how to build what the market wants. Those old technologies don't go away.
People still ride and rise horses.
The rest you can add to the PC at your own risk.