What is a typical scenario when air traffic control (ATC) would flash a white light to a taxiing A/C?

I know it is to return to the starting point on the airport but why? please list some possible reasons and clarify.What is a typical scenario when air traffic control (ATC) would flash a white light to a taxiing A/C?
Light signals are used by prior arrangement if the airplane has no radio, or in case the aircraft's radio fails.





http://en.wikipedia.org/wiki/Aviation_li鈥?/a>What is a typical scenario when air traffic control (ATC) would flash a white light to a taxiing A/C?
well, this is done because the light aircraft has an electrical failure, and therefore the ATC cannot tell the PIC to go back to the starting point...when the aircraft lands, the white light signifies that the PIC can taxi back to the apron they came from and most probably there will be a marshall on the ground to direct the exact route.
Another possibility could be that a faster aircraft is coming in and ATC wants the taxiway cleared.


Or, maybe the pilot left something in the FBO, and the FBO calls ATC to try to catch the pilot before he departs.
Sometimes a stuck microphone blocks the control tower's radio communication frequency, and instructions are transmitted by light signals.