Because it will give more taste to food you cook
it adds taste to the food and it is flavor to the food you cook.
Sauce is essentially a moist or a liquid component, which is served along with the dish to add contrasting and complementary flavours. Apart from adding moistness to the dish, it also adds to the texture of a particular dish and enhances the taste. Sauces also add a visual interest to the entire dish
Sauces play an important role in maximising flavours, adding juiciness and improving the mouth feel of a dish.