Your rivals (whether they make competing products or merely use their success to bid against you for employees) net most of the benefit from your training investment when your trainees aren't going to spend the majority of their career with you.
Great, then the issue is to figure out "how do we create an environment and culture where people will stay here for a very long time?"
Great, then the issue is to figure out "how do we create an environment and culture where people will stay here for a very long time?"