A good question. I have built one once - when with a good friend of mine and trekking up Kilamanjaro - we built a stone cairn for and while thinking about our respective families.
Such a lovely scenic view of the sea and pebbly beach. As for the cairns , I have no idea of their meaning except someone with time on their hands testing their skills - but always intrigued by them ! fav for the view ! fav
@30pics4jackiesdiamond@wakelys yes indeed, that is the big down side, though in this particular case, the stones get moved around with the tide enough anyway.
https://www.sciencealert.com/rock-stacking-might-look-amazing-on-instagram-but-there-s-a-dark-side-to-the-magic