Why would some archaeologists leave small dirt partitions between adjacent dig plots?

Dont get me wrong, thin walls of dirt look cool, but seem like more work for the people in the trench. (Im wondering after seeing a picture of a dig

Dont get me wrong, thin walls of dirt look cool, but seem like more work for the people in the trench. (Im wondering after seeing a picture of a dig with six or so adjacent plots separated by a hand-span of dirt.)

or:Dont get me wrong, thin walls of dirt look cool, but seem like more work for the people in the trench. (Im wondering after seeing a picture of a dig with six or so adjacent plots separated by a hand-span of dirt.)

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