Why is the nucleus located in center in most eukaryotic cells?

The nucleus is the chief organelle involved in cellular reproduction. During the life of the cell, the nucleus also directs the metabolic activity of the cell and helps shape the cell into its final form. Instructions for the synthesis of key proteins continuously pass from the nucleus to the cytoplasm, particularly through the channels of the endoplasmic reticulum. Even the basic material of the protein-synthesizing ribosomes are synthesized within the nucleolus of the nucleus, stored, and then passed to the ribosomes.
These key functions of the nucleus suggest that it should receive a maximum degree of protection. A position deep within the interior of the cell provides such protection. Those cells that developed this arrangement presumably were better adapted and tended to survive.