Do you hang out on the Trail much, these days? In the last few years of section hikes, I'd say close to 100% of the thru-hikers I've encountered (mostly in New England) have been walking with poles.
I'm sorry to say this, but most sales people at "large outdoor stores" don't know diddly about long-distance hiking. And that goes for the fine folks at my local REI and EMS outlets as well.
Poles sure aren't a fad among skiers (alpine or Nordic) or snowshoers or those who hike in snow.
I had hiked for 25+ years without poles. My very first hike with Lekis was from the Dartmouth Coop to Lyme, NH, June 2002. During the first few hours of that hike, I thought to myself, "why did I wait so long to try this?"
I find poles not very useful on easy, flat stretches, and useless on seriously steep stretches. But in that vast range between, and particularly on lumpy ground, they're great.