Your statement would also only be true if people could genuinely identify low performers every single time without causing collateral damage, you are able to always ensure you hire people that are good and the company culture does not devolve into a empire building system and managers are not power hungry people looking out only for themselves. And this happens, it happened at many silicon valley companies (including one I worked for that is well known). Stack ranking does not work. It creates a culture that ends up embodying all of what I said above.