When carbon fiber first hit the scene, Formula One built like every single part they could out of it. Then one of the Ferrari(?) cars bumped into someone else in like '91 and the thing shattered like a champagne flute, leaving the driver (and the motor, and the transmission, and the tires, and the fuel tank) bouncing around on the track like a craps hand. FIA decided that maybe the monocoque should be something that doesn't turn into kibble under force.

I learned that the thing that keeps carbon fiber and aramid composites out of mainstream usage is the inability to non-destructively test it. At the time, airlines were busily swapping carbon fiber 777 components out for aluminum ones because while the aluminum parts were heavier, you could actually magnaflux them and see if they needed replacement, whereas the carbon fiber stuff flies X many hours and is grounded forever. This later became an issue for the Air Force in Iraq.

I didn't buy a carbon fiber frame for my LA bike so hard. As I told my friends, I've only been hit by a car three times and carbon fiber frames can just f'n shatter on you. Which is not what you want to deal with when you need to run Schwalbe Marathons just to keep the flats under two a month.