There are code reviews. At no point did I write no reviews, that's something you inferred.
Both me and LLMs are constantly auditing software.
In-fact auditing and QA is mainly what I do now and human audits become much easier when it's scoped to modules.
This obviously won't fly for "serious" software such as airplane software, but I'm willing to guess that even customers of a low-stakes SaaS would get pissed off if your product regularly turns up new bugs.
I think it's easier to just do code reviews...