The weird thing is, if you, as an employee start to show feint signs of wanting to leave, e.g. by complaining a lot to colleagues, or having an upset look on one's face, usually it is not acted upon, or even not picked up by any manager. If on the other hand you make it very clear that you are unhappy or that you might want to leave, it is understood as you are going to leave anyway, so they don't bother fixing any of the things that you have a problem with. At least that is what I experienced a few times. Instead they start to act as if you don't belong to the team anymore or give you boring or strictly defined tasks. So no wonder, you leave and they find some other employee, in which co-workers need to invest time and effort during a period of about half a year to get them up to speed. Rinse and repeat.