BigJohnD wrote ...
It's about risk and preventative and post-incident actions.

The presence of ESP and auto-activation of TSP when hooking up a trailer/caravan to monitor things like:

differences in tyre circumference,
steering wheel angle,
battery voltage,
clutch pedal sensor (for manuals),
accelerator pedal position,
engine speed,
gearbox information,
vehicle speed,
Longitudinal acceleration,
Lateral acceleration,
roll angle,
yaw,
wheel speed sensors,
electro-valve senors,
brake fluid level,
brake pressure and even the
status of the handbrake.

is the preventative part.

The implementation of the system to stabilise the car's travel is post-incident part.

To have all those inputs activating a system which responds as if no trailer is attached when there is, is too big a risk and could well be construed as contributory negligent by insurers, expert witnesses and courts.

Most people seem to equate adding a tow bar to making sure the rear lights work. It's often forgotten than the whole dynamic of the forward motion is significantly altered. Citroën have gone to great lengths to ensure everyone's safety by incorporating a sophisticated vehicle stability management feature to reduce the risk of unwanted incidents.