There's a lot of reasons. There's a lot of breadth to "software engineering" (FAANG, web dev, embedded, OS, small business, etc.)

I'm sure there are some places where LLMs are bad due to lack of training data. There are some places where the LLMs are bad because the code base is terrible (and there's always "rockstars" at these jobs that severely overestimate their skills because they're always the one fixing the mess... which they also probably caused). Some devs/engineers feel threatened. Many devs/engineers think they're special and super smart so surely no machine can do their job.