Over here that's the brake booster.
I can only think of one reason for electrical connections to the servo - a feature known as Brake Assist (BAS). However, this feature was not introduced until the 1998 model year in the U.S. Perhaps Europe received it earlier?
BAS is a safety feature intended to help drivers better utilize the brakes during a panic stop. A computer monitors the brake pedal for very hard, aggressive braking. When the programmed threshold is exceeded BAS is activated. BAS is basically a two stage power assist for the brakes - regular and extra strength. During panic braking the servo is switched to extra strength mode. The intent is to insure drivers utilize the full braking power of the vehicle to avoid an accident. Apparently Daimler research found that typical drivers utilized only a fraction - 60% I think - of the available braking power when attempting to avoid an accident. BAS makes up the difference.
Perhaps the owners manual will verify whether your car is equipped with BAS?
I can think of only one reason why BAS may be deactivated. If one's driving style is to stab at the brakes rather than smoothly apply them, BAS can be unintentionally activated. This makes for a not very smooth driving experience. Perhaps the previous owner found it annoying?