Because he's paid to deliver code that works. Letting an AI agent do everything would be fine if it didn't make any mistakes, but that's far from reality.

Do typesetters inexplicably change the meaning of the book or document being typeset? Do compilers alter the behavior intended by the programmer, sometimes in ways that are not immediately obvious? Did the invention of typesetters lead to investments so massive, that the investors had to herald the end of handwriting (no equivalent analogy for compilers)?

So I take we can soon replace coders entirely. Just fire all of them. And let some intern under VP prompt the whole thing?

Resistance to technological change has been a thing since farming was invented. Socrates thought that writing will ruin everyone's memory, and that people who just rely on written word will appear knowledgeable while actually knowing nothing.

The only difference is that this is happening to us.

Do typesetters or compilers write the code for you? Or are you perhaps using a disingenuous analogy?