People used to create cairns to mark trails. When I was a kid I used to follow routes from cairn to cairn. Unfortunately, many people knock them over and put up misdirecting rock piles.

But I guess we have GPS ... which is more reliable.

The art of rock stacking was super popular a decade back. There was a little bit of kick back because some people were stacking rocks is relatively pristine areas and trampling down the under growth in the process; so it fell out of favor. It is still fun to find well stacked rocks.