some proteins every meal?

In this book
http://www.amazon.com/Slow-Down-Diet-Eating-Pleasure/dp/1594770603/ref=sr_1_f...

that's mainly dedicated to other aspects of a weight loss diet than what and what not to eat, the author says that there should be always some protein in every meal, doesn't need to be a big amount, but it's better if it's there.
Why is that? do you agree?

So for a trial today I added an egg to the sauteed brown and red rice with zucchine and mung sprouts that I was cooking, and lunch was good, very satisfying. It kind of feels like a good idea to me, it's what they do in Thailand for example. Could be meat, fish, tofu, lentils, added in small measure to a veg & carb meal. There's something like that also in Italy, we call it piatto unico.
Instead of having exclusively protein meals and carbohydrate meals, which is what I normally do, maybe as a reminescence of the old idea of foods associations, that I don't particularly care about. It feels like it's more complete and satisfying. What do you think?