Why is the output table on a jointer adjustable?
Michael Dresdner: Originally, it was to accommodate the changing size of jointer blades, as they were ground down during successive sharpenings. But it also is convenient for those days when you manage to get all three blades at the same height, but not necessarily at the same height as the outfeed table.
Rob Johnstone: As Michael said, its first priority was practical & but, woodworkers being who they are, they soon took advantage of the tool’s adjustability. You can make tapered cuts (that work well for tapering table legs, for example) by clamping a ramp onto the outfeed table. You can adjust the taper with either table.