The superb Kapitalism101 explains a few things. The conclusion I reproduce here:
But labor hasn’t always been like this and it doesn’t have to be like this. There is nothing about labor itself that requires it to be unskilled, repetitive or brutish. But once a change has become generalized throughout society we tend to think that life has always been this way: that labor has always been a commodity and that it is “progress” to attempt to cheapen labor whenever possible. From the perspective of capital this is indeed progress: the progress of making profit. But from the perspective of humanity there is nothing progressive or efficient about wasting human life and potential merely to feed the insatiable appetite of capital.