1. Steel never goes out of style, so no need to chase the latest and greatest.
2. Comfortable ride, better than any of my CF road bikes, especially because I can squeeze in 28mm tires.
3. I get more compliments and questions about my steel bike than all my other bikes together.
4. I get more respect if I win a spurt on my steel frame, since people are convinced it must be a lot slower.
5. If I have an off day I can always blame the frame. If I have a good day it must be the motor.
My Colnago Master weighs around 9 kg, so you can probably save 1-2 kg on CF which will never make any visible difference. After 30 years of riding I have never had a steel or aluminum frame damaged in a crash. However I broke the top tube of my Ridley Noah in my first crash with that frame when I went down and my knee slammed into the top tube. $500 to fix...