Like you were getting at, it's a great counterpoint to the argument that the best use of marginal lands is to graze animals on it for human consumption.
I also think this is potentially a great way to make a cheap protein supplement, especially if you don't have much cash or live somewhere remote that vegan powders are prohibitively expensive or unavailable. 7 pounds for 100 grams isn't cheap, but if you make it yourself with handpicked weeds, the cost is negligible. Even if you paid for the greens, it's still probably going to work out cheaper than something like vega or any other supplement with similar vitamins and omega 3s added.
