Just checked my '21 boxers set, and breaks down as:
No border: 43
Border: 15
Until Adam comes along with a better reason, I'm going with: "They're penny Exhibit cards."
I can just image the head of Ex. Sup. Co. saying to the art director: "I don't give a #$^(&^ about cropping, just get them done, so I can get them in the ^&$%@* machines."