Sometimes, the best reason to do something is "because you can." My wife saved an old, reliable typewriter from the '80s from the trash. It sat in our attic for a year or so, and when it became clear that it was more or less useless to us, too, I decided to give it a USB port. An Atmel microcontroller intercepts character presses in either direction and converts them back to keypresses or appropriately shorts the key matrix on the typewriter. The board was fabricated on an LPKF Protomat S103 milling machine.