Helldritch
Hero
I agree. But read on how death can be made permanent even 1 to 3rd tier characters. Heck, even top level characters can die forever depending on where they die. I am sure Orcus would not relinquish the souls of those that dared to challenge him on Thanatos.One character's death can be but a temporary setback for the party, and even a TPK doesn't necessarily prevent another party from accomplishing the same goal. That's leaving aside the possibilities of raise dead or resurrection, which make death ... not inherently permanent.
Failing to accomplish a goal--having whatever consequence of failure happen--can and arguably should be irrevocable. That Bad Thing you were trying to prevent, you didn't prevent. The world is permanently scarred. For some people, having their character/s live to see the Bad Things happen would be worse than having them die. For others, the possibility of redemption--the possibility of mitigating That Bad Thing, or preventing it from getting worse--would be worth playing on.
But what characters failed to prevent can be mend by another group or the very same group. Failure in D&D is far from being the end. Hope is still there. But death, on the other hand, can mean full stop for a character or even a group. No second chances. But some here deny this.