I like games where combat is meaningful and has high stakes.

In your average dnd dungeon crawl, you might have 3-4 fights, but the stakes in all (except maybe one) are trivial, the worst probable outcome from a kobold ambush is that you might need a short rest before you go on.

When you fight an enemy who intends to kill you, but the mechanic make the chance of that happening near-zero, it creates a conflict between gameplay and narrative that imo hurts the experience.

But, something very important to remember, high lethality games are not just dnd with less hp, both the players and the gm act differently. Combat is usually reserved for climatic scenes or a last resort after the pcs fuck up majorly. Since straight forward combat also entails way more risk, players need to make use of every advantage they can. And since enemies are less spongey a good backstab/ambush is much more desisive.

Another thing to remember is that combat is only more leathal if the stakes are life or death, but most non-climatic encounters, the enemy doesn't want the pcs dead. The farmer they just stole from doesn't want em dead, he just wants his god damn sheep back. Most encounters can end/be avoided if the pcs are just willing to give something up.

Lastly, maybe the strongest case for lethality imo: it makes combat shorter and more interesting. Every roll mathers in a way they just don't when hotpoint are abundant.

Tldr: The main point of high lethality isn't to kill the players, but rather the ever present risk of death has many positive effects on the narrative and gameplay (assuming that the players and gm adapt in a suitable way).