Understanding how to express fractions in different ways is useful in many practical situations.
Cooking:
Imagine a recipe calls for 1/2 cup of flour, but you need to triple it for a larger batch. You would need 3 * (1/2) = 3/2 cups of flour. This is an improper fraction. Converting it to a mixed number, 1 1/2 cups, makes it much easier to measure out in the kitchen (one full cup and one half cup).
Sharing:
If 7 friends want to share 10 pizzas equally, each person gets 10/7 of a pizza. This doesn't make intuitive sense. By converting it to a mixed number, 1 3/7, you know that each friend gets one whole pizza, and there are 3 slices left over to be divided among the 7 of them (assuming each pizza has 7 slices).