Imma leave this here, to help deal with the larger issues at play suggested by the poll (to which I did not respond as a result):
https://dmz2112.blogspot.com/2017/02/dungeons-delicious-fudge.html
But my short, specific answer is that honesty is a terrible trait in a storyteller.
Nobody Very few people want honest stories. Character death, like any other character action, ought to be meaningful.
As gamemasters, we are rightly frustrated when a player trivially circumvents an aspect of our game that we put a lot of effort into, and what is a character if not an aspect of their game that a player has put a lot of effort into? I don't agree that PC death should be taboo, but I also don't think it's a consequence that should be invoked lightly.
This is a relatively new attitude for me. I'm old school enough to believe PC death is an important part of campaign verisimilitude, but I'm old (full stop) enough to have seen what it does to players, and to have felt them feels myself. The result of my calculus is that no, the added 'realism' isn't worth the hassle.
I think the concept of conditional immortality, as described by Andrew Hussie, has some useful implementations in this space, with some modification. I'd post a link, but the relevant wiki page is strewn with inexcusable folly. The core concept is that a PC's death should be either just or heroic, or it doesn't count.
- Bard rushes headlong into a room filled with draconians; just.
- Rogue willingly touches Anarchocles' circlet to the Wand of Orcus, destroying utterly both the Wand and himself; heroic.
- Wizard uses a fireball in melee range atop a fortress wall while carrying an oversized basket of alchemist's fire; just.
- Paladin rolls a natural 1 on his Perception check and has his throat slit in the night by a kobold;
stupid not how I would do things.
So yes, I kill PCs. But /I/ decide when it's a good idea, not my dice. Just like all the other important stuff in my campaign. Random dungeon generators are fun but they make for terrible campaign guides.
EDIT: This is very D&D5 specific, but when my PCs fail three death saves and I don't feel their end would be just or heroic, they suffer a permanent affliction instead, as well as a sanity penalty.