Why is plastic never considered a Premium build material?

[itic]

Last winter i tried to melt my plastic backed nexus 7. Almost pulled it off too. I figure the backing would have been metal or glass it would have done more damage then it did. Anyway still works Ok despite its hardware and support. Had a plastic nexus 5x and that thing could really bounce almost as good as the plastic case my MXPE occupies. Plastics Ok for me...