A very smart gardener.
It's no secret weeds, or any plant for that matter, like water and sunlight. Without one or the other, they die. Using plastic products creates a mess in the landscape. The plastic rips and pretty soon there's scraps floating around.
Cardboard does the same thing and it decomposes so there's no weed barrier legacy to deal with. Spreading a thick layer of mulch over the cardboard holds it in place and cools the roots of new plants.
In a year, plants like the Matilija Poppy, Yellow Spurge, and Blue Oat Grass in this Studio Wildwood design will start to fill in. Then the garden will have a living mulch!