...I've already demonstrated the existence of ASC (which is simply BMW's naming for their early "stability control" system) in 1993, not 1994. But you're keen on ignoring facts.
The rest of what you wrote exemplifies the point: With about 10 years of progress in the field and Moore's law at play, still the Carrera GT apparently did not include any such system.
This is not a technological problem, but a design problem: The Carrera GT already had ABS brakes. It is plain to me that they simply didn't want the extra mechanical complication that comes with such systems.
BMW, for instance, was fond of using an extra throttle body inline with the normal cable-operated throttle. This extra throttle existed only to reduce engine output in response to the ASC's decision of something being amiss. Such "extra parts" and intake restrictions may be frowned upon in an allegedly race-ready supercar, being easily trumped by simplicity, weight savings, and getting rid of any superfluous intake restrictions.
Fly-by-wire throttle gets rid of some of these issues. It is unclear to me if the Carerra GT had that, or conventional cable-operated throttle(s).
Furthermore, you understate the utility of even the early BMW system. Even in 1993, it worked rather miraculously. I've repeatably rounded bends on freshly frozen, sun-polished ice at speeds that would've left most other cars in a ditch (or indeed, even the same car with ASC disabled) without any drama other than a bit of grunt from the ABS pump and the odd sensation that the throttle was not entirely under my own control. The car tracked neatly around the corner with my foot on the throttle pedal.
Low speed example? Yes. Fast forward, add about a decade of computing improvements, and doing the same thing in a much lighter, 600HP car is not so daunting: The physics involved don't care what the maximum engine output is, only that it can be reduced.
BMW used DSC (a later version of ASC) in the E39 M5, which had ~400HP at the crank and eight fly-by-wire throttles. Production of this model was finished in 2003.
Later M5s offered more power, and still had stability control.
So, plainly, the opportunity was there for a higher-powered car to have stability control while the Carrera GT was still in the planning stage. Porsche themselves are no stranger to stability control: They call their own system "PSM."
In conclusion: Either Porsche is inept and, you know, just couldn't figure it out (which I doubt: It takes lots of very smart people and truckloads of cash to get a car like that onto the street), or it was a simple design decision to help foster the notion of the car being a stripped-down, race-ready package of awesome ridiculousness. (Please choose only one.)