Why should a rank 50 not suffer any SP penalty when everyone else does? SP penalty is a horrible idea in this game, it's way easier to die than it was in XI. They would have to change so much of the game if SP penalty was added, to make it less easy to die. Making the penalty for dying weak allows content to be harder because it's no big deal if you die multiple times in a fight or have to retry shit. SP penalty would mean AoEs have to be weaker, mobs 10+ ranks above you would have to stop two shot killing you, among other things. No one would risk high staring leves and people would be less willing to help you with anything difficult.