Time for a little role playing.
You're running a software company. You decide that you want to squeeze your lemons a little harder, to turn your assets into high performing worker bees. So you implement a rank and yank scheme.
Let's pretend for a minute that this isn't teamwork poison. Your team members won't be looking for ways to screw each other over, to avoid sliding down the curve. Let's say it works. Your people actually get better at what they do. They start working longer hours. They are more productive. The threats have an upside.
Then what? Six months pass, and it's review season again. The bar goes up. You can't have everyone doing better, because the curve is still there. So you have to ask for more. Now you have a problem though. When does the bar stop? You have a bunch of excellent performers, but you have to penalize some of them, by definition of your stack ranking system. Now you take a few of your excellent performers and tell them that they're not good enough any more. They need to work even harder.
Obviously, this can't go on for long. These (formerly) excellent employees either leave on their own, or they get "gapped out" - yanked because of their rank. The company down the street hires them and congratulates you on having bred a fine developer that you squeezed dry.