It makes sense, at least in hindsight. How many household devices are available today with an LCD display? My printer cost $20 and has a color backlit LCD that's better than the GBC display. Back then, they saw the usefulness of a display and input system, but it was cheaper to implement this way than to actually include the hardware in the device itself.

I'm sure that there's plenty of "premium" model sewing machines available today with similar functionality, but the hardware is built-in now.