Addy Osmani, the head of user experience for Google Chrome, calls this 'the 70% problem':AI can recognize patterns, but does not (yet?) understand flow mechanics."While engineers report being dramatically more productive with AI, the actual software we use daily doesn’t seem like it’s getting noticeably better."
Also a lot of business applications have to play well with legacy systems, that have a bunch of quirks, that cannot simply be deduced by using AI.
Most of the time that is due to lack of planning and process. Few teams work to coding standards or have dedicated test teams. Worse yet, the art of writing specifications is dead. Most of my clients do not have a clue about how their system should work or the nuances of how they should "look and feel" to the end user. Almost none of them will sit down with me to verify that my understanding of the process/procedures/behavior of their intended product matches their expectations. Fortunately for them, I'm pretty good at this and can sleuth my way through the project.
A decent organization will refine its safety and functionality checklists or feed that back into standards. Few do so.