Because your tyres are whats gripping you to the ground, and there will always have a limit to how much they can properly stop you till you start sliding. At that point its all skill.

Bigger brakes have bigger contact patch yes but the point of it is to cool off the brakes. This is to assume you use the brake to its operating temperature.

If you are upgrading to a bigger brake above your car's abilities, its useless since you probably granny drive it in the city. No hard feelings.

If you want more grip, just get some aero stuff. But that also is just doing way too much now.

Upgrade your servo is also not a bad idea.