As everyone stated above, there are a whole host of reasons why someone would leave their job. I think a main contributing factor is due to mundane projects and day to day activities. I have heard countless times from colleagues that they have left work because what started out to be an exciting task turned out to be repeated day in a day out. These mundane tasks performed over and over again can become rather taxing and can lead to burn out after a while. This can in turn lead to lack of passion for ones work which can then turn into lack of recognition. I feel however a major contributing factor is the mundane day to day activities that can cause one to leave for another exciting opportunity.