Up until the 50s, cars stopped faster than they accelerated. From then until these big brakes started being installed, cars couldn't stop at high performance levels, but the engine tech was there. Not many people were installing NASCAR drum brakes, but were installing HP engines.
While a portion of the customers that are putting them on to impress, a HP brake setup does allow better stopping and more prolonged stopping.

Great braking is needed to survive in modern traffic due to not only the better braking of modern everyday cars, but also due to the stupidity of others out there. You can drive slower, but there is always an idiot or a situation that will require you to stop on a dime.