Gee, here’s a novel idea.......
How about having NO WAY to turn off the Transponders in Aircrafts??
A couple of reasons -- sometimes ATC requests the transponder to be turned off, such as during ground operations (many transponders do this anyway on the ground, without moving the switch to "standby"). And another reason is, you may need the capacity to turn as many components off as possible, in the event of an electrical fire.