Plastic is hands down the best material. Anyone arguing glas is better is an idiot and only care about how it looks. $599 to change a broken glasbackside of an iPhone is really crazy. Metal does not work because it does not allow wireless charging. Both glas and metal is very cold, impossible to hold in winter without a case. Plastic is durable, easy to mold, cheap, lightweight, allows wireless charging. But glas and metal is used instead because it feels more premium and people are idiots.