I worked with a guy who fits this description. If there’s something he can reinvent poorly, he’d do it. A big part of what I did while working on the same team as him was slowly chipping away at his weird domain by introducing standard tools. I always had to advocate for them in such a way that they were solving a different problem, and then slowly work towards a point where some of his homegrown stuff became unnecessary.

As to the job security idea: the only people who do this are people who aren’t good at creating real value, so they have to try to create niches where they’re needed.