You break it when you start to fall down and plant the pole to save yourself. It bends, but prevents you from falling. Additionally if it's carbon,it snaps.
That could happen, too, true. There have been times when I was descending along a rocky trail and the end of the hiking pole got caught in a crevice. I had to be careful to pull the tip out before it broke.
I am not just careful with gear, but with the walking itself. It may sound funny, but I walk as if I were dancing; every step I take is placed as carefully and accurately as possible. I try to make my walking into something artistic and athletic, so that I move both as gracefully as I can manage and with as little wasted energy as possible. No super wide steps as I ascend, no heavy, thumping landings as I descend. I try to keep my legs bent a little and to use my entire gamut of muscles as I walk, so that the progress is smooth and well-balanced. I constantly tell myself to focus on what I am doing and to not get distracted, along potentially hazardous sections, by things like my camera or conversations with partners. These are to avoid injury, to make the movement conscious and deliberate, and to not be so battered at the end of the day that I can'T move well anymore. That is why I go as lightly as possible and why I like wearing trail shoes. They allow me to move gracefully and to not overly rely on my hiking poles for balance and safety. Therefore the poles don't break.
It took a very long time to learn to do properly, but learning to walk the right way has changed the way I see mountains. For instance after learning how to use the tops of the rocks on the trail as a kind of level "walkway" or, when descending, as a kind of "ramp", instead of thumping along up and down over and around the stones, I found that I am able to walk much more smoothly and with less stress on my knees. I can also move quite a bit faster than fellow walkers, without trying any harder. I'm always surprised that no one talks about how to walk on these forums. There's technique to it, but most people just seem to kick along the same way they do in town.
Sorry about the OT post...