What used to be the standard way in American English of complimenting someone on a job well done, viz. “good work!” has largely been replaced by the phrase “good job.” This change in usage is underlain by a shift in the value system, as an analysis of the two variable words reveals.
The difference comes down to the fact that work applies as a noun to the AESTHETIC value of the object resulting from an action. We habitually designate, for instance, art objects as works, not jobs. One can be “good at one’s job” but not “good at one’s work.” One’s work can be one’s job, and in the latter sense job can connote one’s duty, whereas work does not. And so on.
This kind of trip through the connotations of the words at issue will always abut in the conclusion that the accomplished result of what we do when we designate the series of actions as job or work makes the first word concentrate on the acts and not on the product in the traditional usage that rewards the aesthetic value of the product with the designation work.
This value did not accrue in the past to job. Now it does, meaning a hierarchical superordination of the ACTION over the RESULT. In this way, American culture reinforces the axiological dominance of process over result that can be encapsulated in the motto “you are what you do.”