It's all about perspective. I would have more cultivated areas if I had enough leaves to smother more grass. And my existing cultivated areas wouldn't be so dry and weedy if I had enough leaves to give them a good layer. If I had even more leaves, I would till them into another area to start a veggie patch. I don't believe there's any value in or need for repeated tilling, but if you have "concrete" ground, a pile of leaves, and a tiller or can borrow one, it's a great jump-start, let it rest a couple months, then use the following spring. Mulch is also great but I don't have a "mulch budget." Leaves are a free gift that is given annually.