I once had an electric motor that raised the lid of a vacuum chamber. Every once in awhile, the motor would attempt to raise the lid while the chamber was still under vacuum, with disasterous results. So, I designed a switch, more accurately a driver, which used the constant current region of the driver transistor so that the motor woudn't pull itself apart. The only problem was that the driver would go into thermal runaway if the lid was stuck. So, I had to use a second transistor and resistor that sensed the supplied current and to cut off base voltage to the driver transistor under this circumstance.
So, in short, in some applications, the driver needs to supply a current ( active region ) and not a voltage ( saturation region )