Leaf removal during the fall/winter months are a key element in maintaining a healthy lawn. A carpet of colorful autumn leaves may look nice and be fun to play in, but they're no good for grass. They block the light and trap moisture, potentially fatal knockout punches for the unlucky turf underneath.
So when the leaves are falling, blow or rake them away as often as you can. Even after the trees are bare, continue raking out the corners where the wind piles leaves up. If you don't, come spring, the grass under that soggy, decaying mat will be dead. Removing the excess debris that restricts air and water from flowing then allows your lawn to breathe. Leaves block incoming sunlight and promote the spread of disease in your lawn. Whether you prefer to rake, or use a blower, you want to make time to remove accumulated debris.