You expect them to work for you entire of their life because you've give many training course, development, pay good amount of salary etc, but the reality people comes and go, all of your investment in human capital are become useless because you need to spend more money to train the new employee.
This is why investing in human capital isn't good.
Any employers know that not all employees can work forever on them but they can always find another replacement for it. Investment in human capital is never a waste because the company also benefit out of it. And if there are new employees, I don't think there is even a cost to train them.