No one is trying to get rich from working on Haiku. They are doing it for fun, as a passion project. Sure AI would help with velocity but velocity is not the only goal. Journey before destination.

Also: Open source is about relationships.

Reviewing code sucks. However at least reviewing code from humans allows you connect and learn from each other. You get to mentor someone. Build a relationship and trust. They learn and grow and maybe someday can also review other people's code.

Nowadays with lots of low effort merge requests and spam it is already easy to burn out. Now add AI. Yeah, no. Why should anyone review AI slop for free. Why? It is the prefect solution to burn your contributors out.