I have to sign off on the code. When I use compilers and 3rd-party libraries, I choose them very carefully. When I use an AI assistant, I have to check that it produces a good enough quality that I can sign off on it and stand behind it as if it was my own. I cannot do that with large amounts of agentic code, only with small enough snippets that I can overlook and check.

You can put it another way: If my customers lose data because of a nasty bug and it was because there was an error in the compiler, it wasn't my fault (unless I chose some unfinished hobby compiler with no reputation at all). If my AI assistant wrote the bug and I didn't spot it, the bug was definitely my fault and is fully my responsibility.

"It wasn't me, my AI assistant did it" is a lousy excuse.