Why are gres often planted for erosion control?

If the soil is left without planting it naturally dries and can easily be carried away by the air. Water may also carry away the soil, but if u plant gr or other plants the roots of the plants hold the soil firmly to the ground. Wind cannot carry away the soil coz of the gr sitting over it. Water cannot carry away the soil coz of the roots which keep the soil particles together. Hope that I answered your question.