I can't take a carbon-fiber frame to get it powdercoated a different color (the frame will 'melt'!).
I can't put a different (or better) headset on a carbon-fiber frame (they're all 'integrated' now
AFAIK).
I can't 'estimate' torque values when tightening connections on a carbon-fiber frame (that sucks when doing MacGyver repairs in the middle of nowhere).