Because in this case, the vehicle can no longer be steered: while it will slow down, it will also just keep sliding straight ahead. Braking and steering at the same time – that would represent a major step towards enhanced safety.
Only rolling wheels are able to transmit steering forces. The solution therefore lay in an automatic variant of intermittent braking that used to be taught in driving school: alternating between braking and steering, in as rapid a succession as possible. That is precisely what this technology was supposed to deliver – in fact better and more reliable than a human could. A real active safety system.
First attempts were made in aviation as early as in the 1920s. They were supposed to ensure that an aircraft stays on track after landing. The systems used hydraulic and mechanical components. Experiments with such systems were also conducted in cars, but their response was too imprecise or too sluggish.