There are real productivity gains by using these tools right now. Instead of doing 1x your normal work, you can do 5x while still maintaining quality. This is like an accountant sticking to pen and paper because calculators are big and clunky.
In your analogy that calculator would only produce a correct answer 80% of the time, and plausible looking but incorrect ones the other 20%. If that were the case I’d hire pen guy.
Also, if your AI has a 20% error rate, you're not holding it right. You need to spend more time keeping it on rails - unit tests, integration tests, e2e tests, local dev + browser use, preview deployments, staging environments, phased rollouts, AI PR reviews, rolling releases. The error rate will be much closer to 0%.