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.
Thanks, I now have a new fear of carbon fiber. Just checked and thankfully my recently acquired bike is made out of aluminium. I’m also now morbidly curious what might happen to the i3 a few years down the line, as it has both a shit ton of carbon fiber and zero bolts.
Archetypal composite design in luxury vehicle is "make the non-structural stuff out of carbon fiber." It saves you weight, it gives you bragging rights, and it'll never be a problem. A carbon fiber component experiencing zero stress or strain is a new carbon fiber component for the sum total of its projected life. Aside from environmental damage, it will behave exactly the same in a crash twenty years from now as it will fresh off the assembly line. You start carrying math overhead when you put it somewhere structural. Bike frames... crack or they don't, and they ride spectacularly until they do. Generally the people who buy carbon fiber framed bikes don't do it by accident, and they know in the back of their head that mmmmaybe that thing is just not gonna come back from a crack-up. Formula One doesn't let you do carbon fiber structure without the safety aspects being non-carbon-fiber. It may fail? It may fail spectacularly but it won't do so in a way that threatens anyone's life. Motorsport learned that lesson early and often, you don't want to rely on components that will let you down because of something you thought was fine six weeks ago. Here's a thing to keep in mind about carbon fiber - it only absorbs energy so long as it's intact. It ceases to be a part of your crash protection portfolio the minute you exceed its yield strength. As a result, there's little incentive for anyone outside of high performance aerospace to use it in a life safety aspect. Aluminum? Steel? Once you push that stuff past yield it absorbs energy as it yields in a nice, calculable fashion. You can make a "crumple zone" out of metal but a "crumple zone" out of composite might as well be a pile of wine goblets. Push it past its yield and it's cracked eggshells. Which is a long way of saying there's very little in your life that relies on carbon fiber. As I said, even United Airlines got sick of (zero stress) carbon fiber body panels because while the plane is still flyable if a panel shreds at take-off, it's a bad look and with an aluminum hatch panel, you can check wear with a spray bottle and a UV lamp. With a carbon fiber panel you throw it away once it's over a certain number of hours, the end.
Re: your assessment of carbon fiber on luxury cars: I have a Polestar, and it had, for about a week after I bought it, a carbon fiber splitter. One rough bump and it was toast. And cost like 2 grand to get replaced…if I were to do the labor myself. Hence no splitter since week one, since I doubt the next one would last much longer.