But everyone knows how long a mile is, and can imagine a cube one mile long one mile wide and one mile high. Though we can't truly grasp the scale, we can at least understand the magnitude of a value of ~ten million.

But quoting a value of 4.4 x 10^19 liters is meaningless for most people.

"Of course, that's 22,000,000,000,000,000,000 two-liter soda bottles!"

So cubic miles seems like a reasonable unit for this pop-science article, despite the fact that you likely wouldn't use it in a published journal article.