It's easier to work in and it gives order and sense to a garden. You know where you can walk. Raised beds also make it easier to get deep, friable soil, essential for successful root crops. Just like real farmers, vegetable gardeners should practice crop rotation. There are plants that are heavy feeders or notorious for disease and pest problems.
Some examples are tomatoes, corn, and summer and winter squash.
Plants like legumes, peas, lettuces and beans are light feeders. Legumes will fix nitrogen in the soil. Another way to boost soil strength is to plant a cover crop in fall like winter rye. It's a green grass that Ms. Svendsen plants in mid to late October. I actually harvested the wheat berries from winter wheat.