Save backup is just like a trainer. I started using a trainer in Dark Souls 1 so I could make my PvP characters faster, took me around 3 hours to finish them but god damn was it boring doing it. Pretty much removes all the "fear" of dying when you can just boot up your old save.
Considering I just died on an NG+4 no deaths run, this would have removed all of the fear entirely. I had only the Guardian Dragon, The Giant Lord & Nashandra to go to beat the game without dying, Dlion had played his arse off trying to keep me alive in sticky situations, we killed at least 15 invaders throughout that time and it all ended abruptly about ten seconds after entering the Guardian Dragon's boss area. (Son of a bitch did a jump back & then straight fire breathed me, I blocked it out of instinct, breaking my guard and it then hit me two or three more times to kill me...
)
But yeah, in short, that tension, elation and sheer adrenaline I would never have felt if I could just beat a boss, back up the save and then go at it again. I might have failed but I would have preferred to fail than cheat my way through!