When I worked at a very small company we were extremely concerned about this, and so we paid people well enough that they didn't want to leave. All I can figure is that the bean counters just don't understand that churn has a cost.
some places like Amazon operate around the churn. Keep everyone anxious and they won't try to collectively bargain nor ask for raises. They won't be around long enough anyways.
Generally I understand the missing factor to be a control thing.
Th power structure that makes up a typical owners-vs-employees company demands that every employee be replacable. Denying raises & paying the cost of churn are vital to maintaining this rule. Ignoring this rule often results in e.g. one longer-tenured engineer becoming irreplacable enough to be able to act insubordinately with impunity.
A bit bleak but that's capitalism for you. Unionization, working at a smaller companies, or at employee-owned cooperatives are all alternatives to this dynamic.
