Why does cell division remain important to an adult organism even after it is fully developed?

Cell division prevents cancers, and is something that in humans and in other adult organisms as well prevents old age.

There are many more complex mechanisms that contribute to old age and cancers, but if cell division slows down an organism reaches the end of its life.

Every set of cells has a limited amount of divisions it can do. literally every organism from the moment of conception is dying.

cells spend most of their time in interphase