Why do gardeners dig land in their beds in autumn?

1) the destruction of weeds, which are natural competitors of cultivated plants;
2) when digging a large amount of organic substances (aboveground and underground shoots, roots of dead plants, organic fertilizers) is under a layer of earth, where they are actively decomposed by soil microorganisms. As a result, the resulting substances become available to plants;
3) loose soil is better saturated with water and freezes longer.