It's an interesting analogy, but employees aren't cards. One important difference is that employees get better over time, assuming there is a decent culture of communication and mentorship.

Maybe you hired a 7 of clubs, but given time they can gain institutional knowledge and improve their skillset to become a Jack of Spades.

I'm happy there are companies that set attrition metrics as a KPI, it makes it easier for me to hire and build out a technical team for my company.