Exactly! I had really hoped that would catch on, but I only ever saw it on some Nokia Winphones and cheaper Androids. The glass back is one of my least favorite features of modern phones and metal isn't much better (pick your poison: shatter, dent, or scratch). The 5c was also a bit of a callback to Apple's white polycarbonate era and some of my absolute favorite Macs.
I even saw some renders of a translucent replacement back for the 5c inspired by the original fruit iMacs[1]. (Shut up and take my money!)
1: https://9to5mac.com/2013/04/03/concept-imagines-low-cost-iph...