No one willingly creates a do-nothing job, and people are not hired to be useless. In the rare cases where this DOES happen, there's usually an ulterior motive

No one willingly creates a do-nothing job, and people are not hired to be useless. In the rare cases where this DOES happen, there's usually an ulterior motive such as vanity. What does happen with great regularity is that do-nothing jobs evolve: a capable person is hired to do a productive thing, the need for the thing is obviated, but no one fires the person. This is an emergent condition based on limited information: in a large organization it's impossible to know what everyone is doing, and everyone was hired to do something useful at some point, so the default strategy is to assume usefulness. In the case where a person's work is no longer useful, there is no reason for the employee to acknowledge this fact, and so the do-nothing job often continues (paired with powerful self-delusion). So how do you get one of these jobs? You don't. They just kind of grow up around you. However, the correct response in this situation is to evolve your role or quit. If you don't and "coast", then you may find yourself unemployable later when the job is (belatedly) eliminated.