Companies that sell topsoil are not equal. Some provide topsoil that is riddled with weed seeds or polluted. Some do not actually sell soil from the top few inches of land, and this is the soil that has the greatest organic life and that makes topsoil so desirable. Instead, the soil may be lifeless and need organic matter introduced to be useful. Purchase topsoil from a trusted source to prevent most low-grade topsoil problems.
Frequent tilling or compaction from equipment, foot traffic or vehicles breaks down the structure of topsoil that microbes and insects work so hard to build, and kills the plants whose roots are holding it in place. Constant fertilizer and pesticide use further degrades the microbe, plant and insect hierarchy that keeps the soil rich. Soil with poor structure becomes lifeless dust, and will not grow plants or lawns well.
Many homes are built without any concern for the surrounding soil. During construction, the fertile topsoil is stripped away, moved, buried or run over with equipment so often that it becomes lifeless from the abuse. Occasionally, the builder will add a thin layer of topsoil before installing grass, but this is rare. Discarded building materials and chemicals, plus the general neglect of the delicate soil during construction, will make for topsoil around the home that is in dire need of restoration.
Add copious amounts of finished compost to areas with poor topsoil to re-introduce helpful microbes and insect life. Add herbaceous plants, shrubs and trees that mine the soil with their roots, pulling minerals and life-giving compounds to the surface -- to eventually land back on the topsoil when the leaves fall to the ground, thus rejuvenating the topsoil. Allow this leaf-litter organic matter to stay in place -- and be sure to add compost at least yearly -- to help bring the topsoil back to life. Avoid pesticides, fertilizers and tilling to help ensure that the topsoil does not decline.