I agreed until the plastic point. The main reason Apple specifically avoids plastic in many of its products is environmentally based. Since 2005-6, Apple has worked to lessen e-waste, a major component in the poisoning of water tables, plastic islands the size of Texas in the North Pacific and Indian Oceans from the oceanic belt and waste. There are third world countries in which the toxins from disposable electronics have been positively correlated to the increase in overall health and cancer of their populace.
Apple has utilized aluminum as it's recyclable and a natural cooling agent for electronics. They use mercury and arsenic free recyclable glass, and with the exceptions of wires and keys, have eliminated ~95% of plastics in their products.
While I do agree that plastic may be a stronger component at the moment, I would rather not pollute the world more just because I want my first world device to be indestructible.
Fact: Human beings are the only life form on the planet that produces unnatural and non-recyclable waste.
aluminum is hardly a healthy metal to humans either. aluminum is considered a neurotoxin and aluminum poisoning can result from aluminum getting into the water supply (similar to lead) if not properly recycled and disposed of.