Because it revolutionized the way people lived. Humans went from hunter/foragers to mass producing food, saving time which allowed for other things like education, manufacturing, art, etc.
The development of agriculture was called a revolution because it was a dramatic change in that people now had some control over their environment.
Agriculture Revolution is the name received by the time in which large civilisations and large settlements began to exist. As a result of this, these people started changing the environment due to their agriculture activities which involve the destruction of the grasses, the damage and depletion of the soils and resources and the like.
