The important thing for printing of newspaper is speed.
For that, rotary duplicator is used and they doesn’t trim the edges, so there are the BLANK between paper and printing aspect.
(from Asagami Paper Press Center HP)

<<Then, why the BLANK is necessary??>>
Is the viewability the most important?? To tell the truth, we cannot print without the BLANK using a ink jet printer, however, without the BLANK , it is clear that the viewabilityis lost.Like this.

It is too difficult to see this.
I found it difficult to reduce the line spaces to reduce the BLANK.