It's not just nurses.
One of the things I left out of the other thread about "what are they teaching in nursing school
these days" is my experience with supervising co-workers in a different industry. There is a certain percentage of people, so steeped in their own narcissism that they allow their own perception of their job performance to be their only indicator. It doesn't matter if you show them stats, metrics, measures, or even "look at how short your stack of completed items is compared to the two people on either side of you", they will only see what they believe. There is no sense of work ethic, no sense of responsibility or ownership, just a deep seated level of sheltered denial about their shortcomings. Yet they will often solicit long and loud about how they're the Rock Star of the department, the most "brilliant mind" to ever grace the company, or refer to themselves as "Mr. Awesome".
Where does it come from? I don't know. It's probably not exactly pathological, but it certainly is a real problem for that individual and the people they work with. I'm sure that some will eventually outgrow it and smarten up, but I haven't seen it happen yet.
If I had the time, I would invest in some more sociology and psychology studies because this is something that's not just in any industry or any generation, but it is suddenly EVERYWHERE.