All this covered at length elsewhere...but
1. You get rare occasions where the transponder emits a corrupted/erroneous squawk (the identifying code - sorry about the banter and thanks for the hint George.....), so you might need to perform a reboot, and also it might be a good idea that you can isolate an electrical device from it's supply. Lots of aircraft have been lost due to electrical fires over the years.
2. One for an ATCer but I suspect they don't want an alarm blaring out every time they temporarily lose a squawk( the identifying code) for a matter of seconds.
3. One for the techies - rumours of cost/ bandwidth limitations.
Last edited by wiggy; 18th Mar 2014 at 20:46.