Answer
Cells have evolved this trait as a means of continuing the respective species. The G0 phase allows for the cells themselves to decide whether or not the body's conditions are favorable, meaning that there is less chance of having defective or insufficient cell to be made.
Work Step by Step
The G0 phase gives the cell the option of either pausing the cell's cycle until the conditions are right or stopping the process altogether and becoming a terminal differentiation. This means that this cell will never be able to go through the cycle again because the body's conditions are just not right to make more cells. This adaptation benefits the body overall as it means the body will not have cells it can't use due to poor body conditions.
