Whether that matters depends on whether people are eating enough protein. A cursory search shows that most people in the west vastly overeat protein beyond their needs. Yet aggressive marketing has Americans thinking they need more protein.

20g of protein in a cup of cooked lentils sounds pretty adequate to me. At 180lbs, it's only recommended that I get 63g of protein. It's not a challenge. I get almost half that in a single lentil salad including any other plant matter I toss in there with its own amino acid profile.