Why Bother With These Impressions?

What end do they serve?  When we were kids, the windows on the Blue Line subway cars would fog over in winter.  We would trace our names, backwards, in the condensation.  "Kilroy Was Here."  The short story, or the heartfelt poem, as bathroom graffiti.

Or even the small handprint, in primitive red pigment, on the wall of a cave in France, 10,000 years old, and the cave itself completely closed by natural forces from observation for eight of the ten.  Ms. Proto-European of 8000 B.C.E. making her mark, as if it mattered.