Another ill that a missing strap can cause in extreme cases is arcing of
ball and roller bearings in the drivetrain, which gets to be the alternate
path if your battery is grounded to the frame and your starter draws a heavy
load. It rarely happens but is a remote possibility. Arcs do real damage
to the steels used in rolling-element bearings. (Sometimes they even weld them
together.)
For that reason I have mostly connected my battery grounds to the engine, since
the major high-amp electrical load is the starter. The strap then grounds the
rest of the car.
--
George Downs, Bartlesville, Heart of the USA!