I think part of it is that, from eons of experience, we have a pretty good handle on what kinds of mistakes humans make and how. If you hire a competent accountant, he might make a mistake like entering an expense under the wrong category. And since he's watching for mistakes like that, he can double-check (and so can you) without literally checking all his work. He's not going to "hallucinate" an expense that you never gave him, or put something in a category he just made up.
I asked Gemini for the lyrics to a song that I knew was on all the lyrics sites. To make a long story short, it gave me the wrong lyrics three times, apparently making up new ones the last two times. Someone here said LLMs may not be allowed to look at those sites for copyright reasons, which is fair enough; but then it should have just said so, not "pretended" it was giving me the right answer.
I have a python script that processes a CSV file every day, using DictReader. This morning it failed, because the people making the CSV changed it to add four extra lines above the header line, so DictReader was getting its headers from the wrong line. I did a search and found the fix on Stack Overflow, no big deal, and it had the upvotes to suggest I could trust the answer. I'm sure an LLM could have told me the answer, but then I would have needed to do the search anyway to confirm it--or simply implemented it, and if it worked, assume it would keep working and not cause other problems.
That was just a two-line fix, easy enough to try out and see if it worked, and guess how it worked. I can't imagine implementing a 100-line fix and assuming the best.
It seems to me that some people are saying, "It gives me the right thing X% of the time, which saves me enough developer time (mine or someone else's) that it's worth the other (100-X)% of the time when it gives me garbage that takes extra time to fix." And that may be a fair trade for some folks. I just haven't found situations where it is for me.