I think Samsung and other manufacturers can't win there. People complained about the perceived build quality when their flagships had a plastic body. Unless you use harder and thicker polycarbonate (like the Lumias or the iPhone 5c) it's hard to have something that truly lasts. You're left with aluminum, which brings tons of problems (it's easy to bend, scratch, the anodization will fade, it feels cold and it's also slippery, and you need to make way for antennas), or glass.