Recall that apoptosis is programmed cell death—think of it as the cell deciding to self-destruct. So you might ask yourself, why would a cell need to die?
Remember that, in the cell cycle, there are certain checkpoints where a cell may stop and ensure everything is going smoothly. If something went wrong, the cell could potentially become cancerous, in which case it is much safer for a cell to undergo apoptosis rather than risk developing cancer.
Another example would be in the immune system. When cells get infected, cells called cytotoxic t cells go around and force these infected cells to undergo apoptosis in order to reduce the spread of infection.
Hope this helps!
