here is my thought...
you say
Nobody is flying when the batts hit 7.2v anyway
while nobody SHOULD...how do we know nobody is.....
now, the "not too intellegent" flyer who does fly with the batteries too low is flying along...on the edge of mental and electrical control.... and the radio shuts off all by itself, the plane now continues on its merry way with no control straight into a school playground, loaded with kids...
Now what?
if you are a radio manufacturer, would you EVER do anything to even remotely open yourself up to that potenital liabilty?
I think not