Here's why:

* DNA Location: DNA, the genetic material, is housed within the nucleus of eukaryotic cells.

* Replication Machinery: The enzymes and proteins necessary for DNA replication are also located within the nucleus.

* Chromosomes: DNA is organized into chromosomes within the nucleus, and replication needs to occur along these chromosomes.

In prokaryotes (cells without a nucleus), replication happens in the cytoplasm, where the DNA is located.