Bc humans can be responsible for approving / denying decisions in the end. Bchumans have the context a brand new prompt might miss. Bc the most intelligent and brightest and smartest AI ever built will do the wrong thing if given the wrong prompt. It can't presume to know things it was never told or has no way to know
Was the last time you've used LLM two years ago? Current SOTA makes good judgement calls and works well even with shitty prompts. And current SOTA is the worst these models will be.