Why is DNA replication important?
After a sperm (from male) and egg (from female) cell have combined, they immediately start to divide. At this point, the cell is called a zygote.
In order for the cells to divide, they need DNA from the mother. They don't steal it. They just replicate it. For a cell to use DNA, it needs to be in the form of a chromosome, a tightly-packed DNA structure that looks like this:
This process continues on and on until the zygote becomes an embryo, and then a fetus, and then it is born.
So, as you can see, the "zygote" cannot live without DNA, so it replicates it from the mother. There are more examples, but this is just one of them.
Source: Personal knowledge and http://www.cyh.com/HealthTopics/HealthTopicDetailsKids.aspx?id=1613&np=289&p=335