Leaves are full of minerals and once they are added to the garden they feed earthworms and other microbes.
The benefits of a garden mulched like this are the reduction of soil erosion, less weeds to compete for nutrients, and better water retention.
Your kitchen is a gold mine for improving your soil quality! Your morning coffee grounds. Your daily banana peel. All of these things will add something different to you soil in terms of nutrients.
Coffee grounds, when mixed into the soil or compost, will improve your soil structure, tilth, and even help to repel certain pests.