From the article: "To make a ton of regular paper requires 100 tons of water". It hardly seems silly to avoid that cost, fresh water is on it's way to being a scarce resource in many parts of the planet.
It's not a scarce resource in the parts of the planet where the paper is produced, and it is not cost effective to transport water to these places in sufficient quantities for it to no longer count as 'scarce'.
I believe that number is purely the water used converting pulp into paper, not water consumed growing trees. I've heard it's 400 parts water and one part pulp, not sure how accurate that is.[1]