I think that those are not generally seen as desirable career paths, and thus there are no vested interests by various cohorts to break into them and achieve parity. When you consider how materially comfortable working from home, writing code, and sending emails, or working on a research project at a university lab in a tenure-track position is as opposed to doing those "dirty jobs", it should become apparent why the focus is on the PMC sector of jobs as opposed to those "dirty jobs".