One of the main concerns of companies and organizations is getting the highest productivity from their employees, since profits and mostly everything else follows from that. Blue collar workers are most productive when they are adequately trained, and white collar, salaried employees achieve high productivity when they are properly motivated. That takes leadership from the executives, but who trains these executives to be leaders? If they are not natural leaders, then leadership training programs are there to instill the skills and insights needed and employed by effective leaders.
Most leadership training programs begin with the assumption that everyone has the potential to become a leader, it's just a matter of identifying and articulating what leadership skills are and training people to express those qualities. Of course the amount of time it will take to train an employee depends upon the individual, but eventually you will come out with a fully trained leader.