Why do cairns feel so reassuring?

This one's on the summit of Beinn a Chuallaich in Scotland. There's something about a pile of rocks built by strangers that makes a foggy hilltop feel a lot less lonely.
Also, yes, I know: don't build new ones.
Photo: Mick Knapton, CC BY-SA 3.0. Source
@tobias_lind · New contributor
Thank you for the last line. Random cairns off-trail have sent people the wrong way.