I had very limited hiking experience before I set out on my thru-hike. I read about these trekking poles and reflexively disliked the idea: I ain’t walking across America with freakin crotches, like some retiree! Thing is, any serious hiking-tent requires the poles to pitch the tent, because any serious hiker has the trekking poles. So I bought some, mainly for the tent. And didn’t use them for the first week. Then I finally tried them one day and after two hours I couldn’t let them go, I was hooked. I nearly cried when I lost one into the abyss, two weeks before finishing. Why?
If climbing, you can use your arms to “push yourself up” and you’re almost like a four-legged animal. When going downhill, you use them to break your speed and reduce the impact on your knees, angles, hips and… well you’re entire body. If it’s flat, you also get that little extra push at the end of each stride and you’re faster. Most importantly, you dramatically reduce the risk of an injury as you often “catch” your weight on the poles before you roll or sprain your angle. Furthermore, it feels nice for your arms to have an activity instead of just dangling around. Did I mention you grow some sexy triceps and an upper torso?
And finally, your tent very likely requires them anyway. And there is also something wonderfully childish about having a stick that you can poke with.
Lightweight carbon poles are super nice, though they are rumored to have a slightly larger risk of snapping. I broke some expensive aluminum poles (130 USD a pair) and a super friendly day-hiker gave me his brand new ones: Generic carbon poles from K-mart selling at 40 USD a pair and I walked 2000+ miles with them without neither breaking. I walk aggressively with my poles, pushing and slamming them into the trail while catching my falls, so I am not so sure of this rumor of “weak carbon poles”.