Good question. Several reasons.

1. Since the same AI writes both the code and the unit tests, it stands to reason that both could be influenced by the same hallucinations.

2. Having a dev on call reduces time to restore service because the dev is familiar with the code. If developers stop reviewing code, they won't be familiar with it and won't be as effective. I am currently unaware of any viable agentic AI substitute for a dev on call capability.

3. There may be legal or compliance standards regarding due diligence which won't get met if developers are no longer familiar with the code.

I have blogged about this recently at https://www.exploravention.com/blogs/soft_arch_agentic_ai/