Ball speeds are faster off the face
Ever improving manufacture and construction have allowed the face to be really thin and flexible, but strong. The face creates a faster, more powerful rebound; just as Drivers have done for a while now.
The face is designed to flex where you hit it
Most golfers strike the ball below the sweet spot with their Irons, so the construction allows the face, low down, and the sole to flex to produce maximum ball speed when you hit the sweet spot AND the area lower down.
Distance, consistency and accuracy improves
The weight saved off the face is used inside the club to increase MOI. That means that not only does the broader hitting zone mean you’ll hit your distance marker, but the ball will also fly straighter more often.