They aren't useless. They are perfectly capable of accomplishment, but know that taking on more responsibilities or assisting will make them miserable in the long run.
I've seen this with some of the highest ranking & paid engineers/PMs in big tech. I usually give the benefit of the doubt that everybody:
1. Has a sense of autonomy 2. Has a sense of competence 3. Has a sense of relatedness
If at anytime any of these are put into jeopardy, a wonderful tactic is to "be useless". There's many bullshit jobs out there that use you and your abilities for the bullshit job holder's personal gain. This is one of the best tactics to take a stand for yourself in corporate America.