They aren't necessarily worse and more unpredictable. IIRC. hallucination levels for the frontier levels are below equivalent average normal human errors, and they might even be more systematic/predictable to some degree.
But even if they were slightly worse and more unpredictable, they are many times faster and cheaper, for some tasks.
That word 'some' does quite a bit of heavy lifting.
Because there is a ton of work that people tend to perform that falls out the scope of that 'some'. And a lot of work requires alignment with other people, and so on. LLMs don't have agency, despite people hyping 'agents'.
But even if they were slightly worse and more unpredictable, they are many times faster and cheaper, for some tasks.