Why do living organisms replicate itself or procreate
This is a very interesting question but the answer (or as much of the answer as is known) can fill a few books. There are many many signals that control cell division. 

As a horrible simplification, the cell can be compared to a car parked on a slope with a driver's foot on the brake. If she lifts her foot, the car will roll downhill. In the cell, there are various proteins (P53 is the most famous) that have their metaphorical foot on the brake. Various external and internal stimuli can cause these proteins to stop suppressing replication and the cell will then continue its cycle and replicate. 

So, a cell's "natural state" is to replicate, there is a complex network of interacting factors (primarily proteins) that actively block replication in resting cells. When the conditions are "right" (what that means depends on the cell in question) the block is removed and the cell replicates.