That's a post hoc argument - you're presenting a possibility to explain why not minimising attrition was actually rational all along. Its quite well established by now that human decision making is not very rational. Even people who aim for rationality are generally biased towards variables with high measurablility.

The reasoning is that if preventing attrition was so valuable, then it would have shown up via better profits for various businesses over the many previous decades, especially publicly listed ones since their financials are public.

I am sure some businesses got it wrong, and some businesses got it right. And it probably even varies within businesses based on specific roles.

For example, it very well may be rational for a grocery store to let cashiers go if the cost of acquiring and training a new one is low enough that it lets the store compete with other grocery stores since they are operating on razor thin margins. On the other hand, people with specialized tasks in the store such as a butcher or baker or manager might have a better case for keeping them from leaving.

That's the perfect market fallacy, which is also a post hoc justification.