"It's America not Europe, hence why you see old people working in supermarkets shuffling around, they can't necessarily afford to retire."
Generally true, but US aerospace industry workers like those in this article can usually retire early and well. I'm surrounded by coworkers bailing from the company at ages 55 to 60. If they stick around beyond 65, then they've either done poorly by their finances or just like the job.
One guy, our wiring materials expert, was 83 when he retired for his 6th and final (?) time last year. His finances were fine, though he liked the extra income of being a very veteran contractor - his billing rate meant his morning coffee break probably earned him more than I got in a day. Very cool stories from him: stuff from the Korean War, early development of ballistic missiles, and even the coloring of warhead wiring (Hollywood, surprisingly, always gets the wire colors wrong when wiring need to be snipped to save the city and love interest from nuclear annihilation.) And he was here because he liked the job. Staying at home drove him stir crazy, and being in close quarters with his wife of 65 years drove them both crazy. So, he kept working. Heck, while I worked with him, two of his eldest kids retired (early, before 60) from law enforcement jobs.
I'm willing to bet anyone repeatedly patted on the back for being the "last original Voyager engineer" and having irreplaceable knowledge of its software was similar. He could've retired, but stuck around because he liked the job (and could bill at insane rates).
"So this 80 year old guy has been working for almost a couple of decades into retirement age and a "replacement" was only brought in 1 year ago (linked article)"
That's a good point, and all too common. My retiring coworkers tend to be leaving with no replacements in line for them, not until the last minute. I understand why: it's expensive to support a replacement doing the same job at the same time that a highly-paid veteran is still on staff. But it's a perpetual train wreck as the replacements stumble for lack of education from the pensioners they're replacing.