Otside of high temperature applications, engineered plastics are the equal of metals in strength in all cases. Even to being used as engine blocks. There is no strength advantage in this application.

Coolants are recycled, rejuvinated, and reused multiple times, ultimately ending up as thousands of drums of hazardous waste. They are not recyclable in the way you describe.

Aluminum chips mixed with coolant and other debris are hauled away for recylcing where they are melted in a furnace, and the organic components of the debris and coolant are released into the atmosphere. The melted alloy is blended into other alloys, and is for the most part recovered, all at a high energy cost. That energy makes it's own contribution to pollution.

Engineered plastics can be recovered reground and reused up to seven times in increasingly lower grade applications, all at modest energy cost, and are at least as recyclable as the coolant, but with no ultimate hazardous waste component.

15 years of manufacturing experience with aluminum alloys, stainless steel, cast iron, hastalloy C, and a wide range of engineered plastics in the development and marketing of industrial devices are the experience base on which this information is drawn.

Investment casting and other techonoogies with metals can produce a net shape part with no machining necessary and no waste, at costs in energy far below total machining. But there is a major investment in tooling to accomplish this, and if you do not expect a long run, there is no payoff. 

Either Apple lacks confidence in the design, or they simply don't care about being green when it comes to the case.

The aluminum milled away is not waste. It is re-used, which you would have known if you had only bothered to find out. Many milling processes mill away more material than is left in the product. Thefluids are also recycled.

Also, no, the injection plastics are NOT as strong as this, use no less material, cause more pollution, as they are often made from organics, in a highly chemical wasting manner.

Too bad you know nothing about this..

If you cast it as only two possibilities, green components and a dirty case, then maybe it would. There is pleasing many people by being altogether green.

Does it really make sense to you to take a 2.5 pound block of high value aluminum alloy and machine away 2 pounds of it as waste chips, waste coolant, worn tooling, and trash, in order to produce a 1/2 pound aluminum case, when a similar case could be made of injection molded engineering plastics with equal strength, less material, and almost no waste?

It is simply ridiculous! It's style not green. At Apple style has always overruled good design.

Why not tell us their side of the story too.. Most of us have already read the apple press releases you just copy and pasted.