Replacement cost is often quite high for any employee, even someone working a basic job, as training is expensive.
Thus why many employers don't do training other than the bare minimum - why train someone who might use the training to go elsewhere. This is the "keep them dumb and stupid" approach to employee retention.
Meanwhile, the employer keeps a bunch of "dumb and stupid" employees that they refuse to make better. Those employees that are self-starters will make themselves better and, if they want to, will leave anyway.
Seems kind of silly to me. If your better employees regularly leave your company, than you probably have more deeply-rooted organizational problems that need fixing.
Thus why many employers don't do training other than the bare minimum - why train someone who might use the training to go elsewhere. This is the "keep them dumb and stupid" approach to employee retention.