What is the cost to companies of letting demoralized employees stick around to wait for options/RSU/bonuses to vest? I'm in the process of leaving a company now

What is the cost to companies of letting demoralized employees stick around to wait for options/RSU/bonuses to vest? I'm in the process of leaving a company now where I've been watching this happen for the better part of two years, and I keep wondering how much more productive and successful we could have been if those people had been let go and filled with some new, motivated recruits.