Some parts lend themselves to additive manufacturing, others to subtractive manufacturing (i.e. machining), some extrusion, molding, etc. ... my point is, just because you can make it with additive manufacturing does not actually mean it is the best way to make the part. You use the right tool for the job, mmkay

The benefits of AM have been covered in this thread already (rapid prototyping, unique geometry not possible to manufacture with other techniques, etc.), and a lot of it's inherent limitations (although many have not even been brought up ...). There probably is not a lot of printing of cassettes for rapid prototyping purposes ...