I am sure it has to do (alot) with the activation of the DSC and DTC, since these 2 systems are based mainly on the rear brakes.
When I bought my car, the CBS was showing 50.000 kms for both front and rear brake pads. Now, after 13.000 kms the CBS indicates 70.000 kms (!!!!) for front pads (have NO idiea how on earth this happened....maybe the pads are regenerating...LOL!!) and 22.000 kms for rear pads.
The DSC (antispin mainly) works overtime around the area I live, since we have very slippery roads.
2011- : BMW 116i (F20)
2009-11: BMW Z4 2.5si (E85)
2007-09: Mini Cooper S (R56)
2005-07: BMW 325ti (E46)
2004-05: BMW 318i (E36)