I'm confident enough to tout this number as effectively true, though I should mention that no company I work with has so far been willing to delete a whole day's work to prove or disprove this experiment yet.
Long ago when I was much more tolerant, I had a boss that would review all code changes every night and delete anything he didn't like. This same boss also believed that version control was overcomplicated and decided the company should standardize on remote access to a network drive at his house.
The effect of this was that I'd occasionally come in the next morning to find that my previous day's work had been deleted. Before I eventually installed an illicit copy of SVN, I got very good at recreating the previous day's work. Rarely took more than an hour, including testing all the edge cases.
I don't have a big sample size, but 2/2 of my first embedded jobs both used network shares and copy+paste to version their code. Because I had kind-of PTSD from the first job, I right off asked the boss on the second job if they had a git repository somewhere. He thought that git is the same as Github and told me they don't want their code to be public.
When they were bought of by some bigger company, we got access to their intranet. I digged through that and found a gitlab instance. So then I just versioned my own code (which I was working on mostly on my own), documented all of it on there, even installed a gitlab runner and had a step-by-step documentary on how to get my code working. When they kicked me out (because I was kind of an asshole, I assume), they asked me to hand over my code. I showed them all of what I did and told them how to reproduce it. After that the boss was kinda impressed and thanked me for my work. Maybe I had a little positive impact on a shitty job by being an asshole and doing stuff the way that I thought would be the right way to do it.
Edit: Oh, before I found that gitlab instance I just initialized raw git repositories on their network share and pushed everything to that
Well, I was severely depressed and was on sick leave for quite some time, but when I was there I just did my job as best as I can. I am not an inherent asshole. I just get triggered hard when some things don't work out (no initial training, barely any documentation, people being arrogant). I just want to be better than this myself.
There are many reasons. First a manager is not a peer but brings in a sense of authority into the mix so the discussions will not be honest. Manager's inputs have a sense of finality and people will hesitate to comment or override them even when they are questionable.
There are human elements too. Even if someone has honest inputs, any (monetary or otherwise) rewards or lack of them will be attributed to those inputs (or lack of them).
Overall, it just encourages bad behaviours among the team and invites trouble.
These should not happen in an ideal world but as we are dealing with people things will be far from ideal.
Anyone who has made seious use of Microsoft Office products in the 00's and 10's knows these things to be true (or they reflexively click save every 5-10 minutes).
Probably a bit of both, but hindsight helped. It doesn't usually end up exactly the same though. Regardless, whatever I wrote worked well enough that it outlived the company. A former client running it reached out to have it modified last year.
The effect of this was that I'd occasionally come in the next morning to find that my previous day's work had been deleted. Before I eventually installed an illicit copy of SVN, I got very good at recreating the previous day's work. Rarely took more than an hour, including testing all the edge cases.