Why to study about employee satisfaction?

In my point of view, the study of "employee satisfaction" helps the company to maintain a standards & increase productivity by motivating the employees. this study tells us how much the employees are capable & their interest at wok place? what are the things still to be satisfy to the employees. although "human resource" are the most important resources for any organization, so to study on employees satisfaction helps to know the working conditions & what are the things that affects them not to work properly. always majority of done by the machines/equipments but without any manual moments nothing can be done. so to study on employee satisfaction is necessary.