Rof certain microorganisms which produce acid. Acid prevents spoilage. There may be spoilage and changes in texture. Sugar sweetens, tenderizes, and causes outer surfaces to brown during baking. Sugar also delays drying out and may increase the volume.
Salt adds flavor.
Less sugar may result in less browning, less tender texture, greater tendency to tunnel, greater tendency to dry out, and a less sweet taste. Less fat may result in a less tender and dry texture and a greater tendency to tunnel. Reduced salt may affect flavor slightly. Keeping time will be shortened. Fat separates the flour or starch granules to prevent lumping during cooking.