So they can justify charging $150 for the poles... No one would pay $150 for walking sticks.
I don't call it trekking, but the deuter people call their big packs "trekking" packs.
To me trekking sounds like a long trip, at a minimum an overnight backpacking trip several miles in. A day hike, even a long one, I wouldn't call a trek.
A 20 mile backpacking trip? A week long AT hike? That's a trek...