ricotta is not really a cheese, it is a cheese by product, like cottage cheese. It will not get gooey when heated...it will separate into tiny curds and thin watery whey. To make it custardy you add eggs. Prevents the separation. Does this mean that all recipes go this route? not at all. but if you are using veggies with some water content...ie mushrooms, zucchini, spinach, etc, it is a real good idea to use the eggs to avoid a watery fall apart product.