They save time and money.
Compared with a lawn, there's no mowing, little weeding, and minimal, if any, watering or fertilizing once the plants are established. And unlike with many fussier plants, there's little need for deadheading, cutting back spent growth, dividing, or replanting.
They're great mimics.
When planted in large swaths, groundcovers can give you the openness of a grassy lawn but with more texture. Small drifts of three or more plant types can give the layered look of flower beds but without the boom-and-bust cycles of annuals and perennials.
They ease transitions.
Groundcovers create attractive buffer zones between lawns and natural woodland areas. They also soften the look of paved surfaces when used along pathways, patios, driveways, and retaining walls.
They control erosion.
Massed plantings tend to slow the movement of rainwater down a slope while the foliage cushions the punch and the roots help bind the soil and absorb moisture. Plus, you don't have to worry about slipping as you tend the plants since there's barely any actual work to do.
Shown: Flagstones surrounded by a blanket of thyme serve as an informal walkway.