Maybe because so many limbs can be replaced by prosthetics and the prosthetics look like real limbs
There's heaps of people with missing limbs.
Well, since lightsabers cut so well, I think that once the first cut is done and therefore the loser is disabled, the winner would usually proceed to cut the remainder into pieces small enough to ensure death of said loser, and (b) facilitate the disposal of the corpse of said loser.
But when they get disabled it goes bad (sad I don't like sand sounds)
Its like a sick horse: head off - problem gone