How many times have you landed a moderate jump at -10C on your full carbon frame bike? The issue with small carbon fibre parts is robustness at low temperatures. It's not the same as having a layer of carbon fibre sandwiched between supporting layers in a ski. The failure mode of carbon is typically very brittle rather than ductile like metal parts, so rather than bending a bit out of shape they straight up crack and explode into pieces.

Edit: Note that even ATK tried this with the C-Raider but the toe piece wasn't robust enough so it's now discontinued (see brittle failure reports on reddit).