What would happen if our cell did not divide?
We'd all die.
If we were a newly fertilized egg, we wouldn't develop. We'd stay that fertilized egg.
If we were a full sized adult, we wouldn't heal wounds, wouldn't replace cells (you lose about 40,000 skin cells every minute - so you'd run out of skin in a short time if you didn't have cell division).
Couldn't make babies....we'd all die.