Bridge plate size. Why so large?

[Bax Burgess]

Is its purpose merely to prevent damage to the top from ball ends, or is there an additional benefit?

[mirwa]

The main purpose is to stop ball ends from destroying the soft spruce top.

Secondary purpose is it can add stiffness into the bracing underneath, some manufacturers make really big bridge plates to stiffen the area behind the internal x brace, which in theory reduces distortion of the guitar top

Steve

[Hot Vibrato]

To add to Steve's point, the added stiffness helps reduce top rotation. Bridges on guitars with smaller bridge plates definitely have more of a tendency to lean forward.