Evans had a good eye for little details that made an image interesting as well as a natural ability to compose and crop out in camera all extraneous details.
When looking at many of his photos you cannot find a single aspect that does not belong or does not make the image stronger then if it was excluded.
One interesting aspect of Evans is that he knew most of the movers and shakers in New York publishing as well as people such as Edward Steichen when he started the photography department at MOMA. IIRC from one of his biographies there were some pretty derisive comments about his work in a letter to Steichen from one Ansel Adams.
Sometimes you can spot how Evans' eye for detail worked multiple times in one scene.
Remember the famous photo of the staircase, with each step having a bumper sticker for
"Royal Crown Baking Powder"? Look to the right in this other famous Walker photograph:
I recall reading (I think it was in "Walker Evans At Work") how he drove the printers at Fortune magazine crazy. He took his large format negatives and used scissors or a knife to cut them down to a precise cropping. Apparently he didn't always get the negative squared.
I've only seen Mr. Evans' work in book form ("American Photographs" and "First and Last") and online at Library of Congress. While there were many truly outstanding FSA photographers and photographs, there is something very special about Evans' work that cannot be put into mere words. To me, he saw and captured things often missed by others. To me this particular photograph was a tribute to the craft of portrait photography, to photographers such as the aforementioned Mike Disfarmer (The Heber Springs Portraits) and numerous others that captured the faces of America. In that one photo, he captured what would amount to today's social media (Facebook) and gave Americans a composite look at themselves. Something that they all could readily indentfy with long before today's mass media came along.