Rock cairns mark the route, for good or bad
Human-built piles of rock to aid landscape navigation have likely been around since the Stone Age. Leave them lie, I say.
Cairns are one of those both-sides things: I love them when I need them, but hate them when I don’t.
In this case a cairn is a pile of rocks, often built unofficially to mark a route, which may or may not have a trail.
When hiking cross country, hikers build cairns to mark a turn, to help them find their way back, to tell Joe they have already been that way . . .
Not everyone likes them.
Some cairns are official navigation tools built by the pathfinder/builder of the route. In featureless terrain, when you come upon a cairn, you look in the anticipated direction of travel, spot another cairn and travel to it. This repeats until the route becomes more obvious.
For unofficial cairns, you don’t know who built them so you don’t know what the builder was trying to communicate. Does the cairn mark the way you want to go, or does it mark the way you don’t want to go?
I have used them both to stay on route, and to mindlessly blunder off route. Thus the mixed emotions to cairns.
I have built them sparingly, usually to mark a turn I didn’t want to miss. I try to remove them when I leave the area.
I leave cairns built by others standing, not so much because they may help other hikers find a route, but because it would take too much effort to remove them.
Building a cairns has an environmental impact, from disrupting the habitat of living things (especially plants and insects) by relocating a rock, to sending more footprints past them. Use them sparingly.