It is generally believed that career progression (specifically the opportunity to earn more) involves taking on additional responsibility which includes supervising and ultimately managing people. As such, given the opportunity, people who are looking to ‘advance’ will put themselves forward for these positions when they become available.
Most people, however, have no interest in managing people. Managing people is difficult – it involves patience, empathy, tough discussions, tough decisions, towing the company line during difficult times despite not agreeing with the direction, listening to people’s problems and excuses, and so on. How many people honestly want to do all of that? Few. As such, it is no wonder strong managers are hard to come by.
If you have employees who genuinely want to manage people, invest in them! Get those employees the coaching and training they need in order to grow in to the position. They are the ones who will be best suited and can be taught the ins and outs of effective managing. Having the desire to manage is key to the ultimate success of a Manager. What cannot be taught, is how to genuinely want to manage people, so putting people in to the role of Manager who do not have a desire to do it, will not work out well.
If you are an employee wanting to advance in your career, and you have no interest in managing people, look at other ways to take on responsibility and to contribute which will increase your value to a business without having to manage. It is possible you might not earn quite as much, but you will almost certainly be better and happier at what you do.