This page explains why.
Inductors behave to electricity as mass does to a mechanical system.
Inductors resist change in current flow, just as masses resists change in physical movement. In the same way, if you suddenly try to stop the current flowing in an inductor - the inductor will resist the change in current. The same way the mass of the car resisted the mechanical stopping, so will the inductance of the coil resist the stopping of the electrical movement - the current flow. When the car hits an object - the momentum is changed into pressure. This voltage will cause an arc across the switch that is interrupting the current.