Originally posted by matteni:
because stopping distance was not being improved.
Stopping distances are generally limited by your tires, not your brakes. Even stock brakes can stop you up to the limits of the tires*. However, doing so on the track can generate a lot of heat. Depending on which pads and rotors you're using, this can cause pedal fade and/or shudder and/or warped or cracked rotors. The primary advantage of the big brake systems is that there are bigger rotors and pads to better dissipate the heat.
* If you use track tires, with their greater stopping capabilities, this MAY mean that the stock brakes are at their limits, in which case the upgrade to bigger brakes can actually result in shorter stopping distances.