The difference makes the necessary barriers different.

There's benefit to letting a human make and learn from (minor) mistakes. There is no such benefit accrued from the LLM because it is structurally unable to.

There's the potential of malice, not just mistakes, from the human. If you carefully control the LLMs context there is no such potential for the LLM because it restarts from the same non-malicious state every context window.

There's the potential of information leakage through the human, because they retain their memories when they go home at night, and when they quit and go to another job. You can carefully control the outputs of the LLM so there is simply no mechanism for information to leak.

If a human is convinced to betray the company, you can punish the human, for whatever that's worth (I think quite a lot in some peoples opinion, not sure I agree). There is simply no way to punish an LLM - it isn't even clear what that would mean punishing. The weights file? The GPU that ran the weights file?

And on the "controls" front (but unrelated to the above note about memory) LLMs are fundamentally only able to manipulate whatever computers you hook them up to, while people are agents in a physical world and able to go physically do all sorts of things without your assistance. The nature of the necessary controls end up being fundamentally different.