15VDC power supply instead of a 12VDC power supply


A 15VDC power supply was supplied with my Velleman K8200 3D printer.
Can this be explained as the controller and all other electrical components are suitable to work on 12VDC.
This seems not good to me as the electrical components are unnecessary suffering.
Why is this as the electrical equipment works on 12VDC and not a range that is between 12 and 24 volts for example?