I'd also add, that in 30 years time, I wouldn't mind betting that it will be easier to make a C64 joystick than find a USB connector. Look at interfaces like IDE, FireWire etc coming and going. USB continues to evolve, too, e.g., with miniUSB, microUSB, USB-C etc. It's a fools errand to try to predict this, in my view. So we keep things simple and pure as we can, but make sure people can make all these add-ons over time. We don't want you being too bored, in any case
Paul.