Originally Posted by cyberkaa

Improves how? Stickiness?

Say the force from your foot/hydraulic system is constant.
The brake pad isn't accelerating, so it's pushing back with equal and opposite force.
Force_friction = mu * Force_normal
And the normal force is what your hydraulics are putting out.

Notice that area plays no part in braking force (stickiness) in an ideal system.

The coefficient of friction, mu, does, which is why you get track pads.

In a real world system, things change. Specifically, you have to consider heat. Bigger rotors are slower to heat and cool, which gives consistent braking.
In fact, if you compare upgraded BMW rotors between different models, sometimes the only spec that changes is that the rotors are thicker.

One benefit to a large pad area is that you don't have to change pads as often if you keep the same thickness.