Now the questions not addressed is why were the keys not collected when the employee retired and if they were, why they were not returned to the office for which one was required.
This kind of thing is common with government and quasi-government organizations. We could really use a taxonomy to help clarify "this kind of thing", but academia has really let us down in terms of that kind of useful and advanced research, especially if it undermines their ideology. In some cases, the incompetence looks like a linear or additive worsening of generic incompetence you'd find even in the private sector. In other cases, there seem to be wholly unique categories of incompetence and inefficiency in government agencies that we don't find in the private sector.
Generalized apathy seems like a recurring issue. I don't know if that's a matter of degree worse than private sector averages, or substantively unique. Especially in the northeast US there are stories of rail workers, transportation workers, and the like who simply don't show up for work for years, or rarely. There are different angles there. The key seems to be that pockets of apathy and sloth can exist for decades in such a way that incredible things are tolerated that simply aren't in the private sector. A lot of people drawn to those jobs just want one job or employer for life, they want it to be pretty much guaranteed, and they just want to sort of exist, comfortably, for life, with minimum effort. There will always be a selection bias issue with jobs that have extreme job security, and it won't generally select for the best and most proactive workers. Proactive workers will be acculturated over time anyway.
I always found it weird that people make so many excuses for the postal service, and have this denial of reality regarding government agencies and the culture and psychology they reliably foster. It's now 2022. The formal economics here was mostly nailed down by 1950, and you don't need formal economics to grasp the human dynamics of coercive monopolies, government agencies, etc. Reality is what it is, and no one knows how to make coercive monopolies efficient and high performing over the long term. I assume people know the story of Lysander Spooner and the American Letter Mail Company – he was frustrated with the post office monopoly, put up a shingle, beat their prices (and probably their service), so they got Congress to shut him down and formally lock down their mail monopoly. I can't imagine any excuse for a coercive monopoly on letter mail, or really anything. It matters less these days, except that they use their mail monopoly to help undercut private carriers on package rates. It does get frustrating sometimes though because they put packages in our mailbox (cluster) that cannot be removed – incredibly, the carrier's rear box opening is larger than the resident's front opening, so objects can be inserted through the rear that cannot be removed from the front... When that first happened in 1880 or 1909, it should've been a Doh! moment, fixed forever. But not with these guys. And you can't call anyone to tell them. 1-800-ASK-USPS doesn't actually enable you to ask anyone anything – every branch in their phone tree dead ends you with no way to talk to a person. I've never encountered a service number that did that.