I don't eat the carbs for the carbohydrate. Half a pound to a pound a day of spinach, celery, lettuce and their ilk won't add a whole lot of carbohydrate, but they add a lot of bulk and interest to the diet. That can slow down consumption, which might increase satiety, and I find that it also makes the food more satisfying--if I eat very boring food, I might not want to eat much of it, but I'm more likely to be on the lookout for something more interesting--and maybe less helpful to my goals--afterwards.