Only some of it's a lot bigger than buckshot. And some is a lot smaller. The hazard from pieces bigger than buckshot, or even the size of buckshot, is great. A piece the size of a marble has the kinetic energy of a 400 pound safe at 60 miles an hour. It leaves us only one choice.
Every space mission chances it.
Every single mission is a lottery. A game of chance. Any piece of space debris, even one the size of a pinhead, can ruin a spacecraft. At millions of dollars an ounce, you can bet there are very few ounces 'wasted' on backup systems. There may be multiple computers for backup, but generally there is only one thruster in each direction, one antenna, and one of most parts.