What's wrong with plastic? People seem to hate it in laptops and phones, but it has several advantages and only few disadvantages compared to glass and metal. It's lighter, cheaper, and usually protects innards better. I used to have Lumia phones with plastic cases for years, and they survived many drops - usually landed on an edge, which ended up with a dent, but not much more. The only advantages I see in other materials are aesthetics, heat conductivity (metal only) and scratch resistance (glass only).