What is the purpose of grass?
Grass plants develop fruit called grain which feed much of the world and yet have green leaves and stems not digestible for humans that are the main food source for animals.Grasses can also be used for building materials, medicines, and biomass fuels.

Lawns are a common feature of private gardens, public landscapes and parks in many parts of the world. They are created for aesthetic pleasure, as well as for sports or other outdoor recreational use.

The Environmental Benefits of Your Grass. ...

Maintaining a healthy, thick lawn also benefits the environment. Unlike hard surfaces such as concrete, asphalt, and wood,lawn grass helps clean the air, trap carbon dioxide, reduce erosion from stormwater runoff, improve soil, decrease noise pollution, and reduce temperatures.

Like all living plants, grass takes up carbon dioxide and releases oxygen. ... 

Grass not only removes carbon dioxide from the atmosphere, but it also traps dust to keep it out of both the air and your lungs. Less dust blowing around means easier breathing, but also cleaner cars, cleaner houses, and cleaner windows.
Grass does not produce much net oxygen because of the type of carbon it produces. When grass dies, its carbon products—sugars and starches—use up oxygen and release carbon dioxide when it decays. If an animal eats the grass, oxygen is used by the cow's digestive process to turn the grass into energy

Improves water quality and prevents erosion
Soil and grass share a variety of benefits. The soil provides nutrients while the root system of grass provides stability for the soil. ... Grasses have a dense network of roots that help trap and remove pollutants from water as it moves through the soil.