Because in most organizations, hiring comes out of HR's budget. Raises come out of departmental budgets. On paper, it looks like it saves money to the accountants.

It's stupid, because companies don't bother to track how much they waste on losing trained employees + damage done by inexperienced ones during onboarding. But that would be hard to track with robotic, sterile metrics, and God forbid executives actually trouble themselves with knowing how their business functions