Why is regualtion of the cell cycle important?

Regulation is necessary so that cells don't either mass produce or make faulty copies of themselves and cause harmful effects on the organism itself

Explanation:

If the cell cycle were not regulated, cells could constantly undergo cell division. While this may be beneficial to certain cells, on the whole constant reproduction without cause would be biologically wasteful.

Then internal regulation of the cell cycle is necessary to signal passage from one phase to the next at appropriate times. This regulation is not achieved through strict time constraints, but rather with feedback from the cell.