Part of the reason my job needs to exist is to address lack of adequate staffing levels and dysfunctional inter-departmental practices. I would say the company I work for is transitioning between one that is haphazardly run to one that is more professional, but that transition doesn't happen overnight, and you need people to pick up the slack during that transition.

Very true. From what I've observed, it's because a firm with This Guy allows that role to absorb all the odds and ends that pop up and need handled, while allowing specialists to focus on what they do best, maximizing their work output and general work satisfaction.

A firm without This Guy means that more small problems/needs get ignored since it doesn't clearly fall into anyone's scope of work or warrant the cost associated with the specialist. And if it gets large enough to not ignore, a specialist will consistently have to context shift to something outside of their specialty when something tangentially related pops up. This decreases their productivity considerably, decreases their satisfaction as they can't focus on what they truly enjoy doing, and increases business risk as things get overcomplicated or slip through due to a more biased view on the strategy to perform the work (based on whatever the individuals specialty is).