Because the job changed out from under them - it's now to use AI as much as possible and generate so much and so convoluted content that humans have no chance of keeping up the "velocity" without being entirely dependent on it.

Because the job itself has now changed, and they haven't. Their output speed might have been eclipsed by that of the engineers who efficiently adopted the new tooling.

Where I work, the power dynamics have shifted wildly. There are a number of senior engineers who refuse to touch the stuff, and as a result, they can barely keep up with their peers. Some of our juniors are now running laps around them.

When a stranger to your craft can now teach themselves what you know, how to do your job, and even how to automate your tasks in the span of the same workday as you, all while reliably being able to gauge the innacuracy of the output they're reading, how much longer do you really hold relevance?