The department that I run.
The data I have is that they're unsupervised, and that they're blowing off enough that it's seen as a problem across the board, and not with some individuals.
I would absolutely say that if 20% of the employees are doing that there's a problem with their management. Probably some need to be fired, likely some or most can be recovered, but with no supervision they're just doing whatever the fuck they want to do. The company doesn't give a fuck about them, and so they give 0 fucks about the company. You seem to think that loyalty is automatic, it is not, it is earned by valuing your human assets.
Additionally, we're not talking about general office help or unskilled labor here, we're talking about skilled tradesmen. I've worked in and around that environment for 25 years, in at least a supervisory role for 15 of those years, as a skilled tradesman for the other 10, at my current employer for 8 years.
They've got a team of highly skilled employees that presumably do good work (since quality isn't the complaint). It takes a lot of time to fill highly skilled positions, and lots of time to bring new employees up to speed with the requisite institutional knowledge. It is, in fact, very expensive to replace skilled workers. It makes sense to correct behavior rather than throwing the baby out with the bathwater.
"Fire all of them" isn't just ill advised, it's outright stupid kneejerk advice. It completely ignores the reasons why these people are doing what they do, and completely ignores the fact that they're currently unsupervised. The right advice is to properly manage them, keep the valuable skills and knowledge, and make an informed decision to fire the ones who don't get it.
For the record, employee acquisition and retention is something that I'm trained in at least yearly to keep with the current trends in IT, where I have to maintain a highly skilled and engaged workforce. It's not something that I'm unfamiliar with, and I'm way above industry average in all of my metrics because of that.
I've seen, first hand, what kind of team the "fire 'em all" style of management gets, and it's a miserable work environment with low morale and unproductive people who do shit work. Nobody who's worth a damn stays around, people who can perform don't. I've heard these idiots lamenting the fact that everyone is lazy and disloyal as their companies struggled and/or underperformed. There's one thing all of those 'lazy' employees had in common...