In Somatic cell nuclear transfer why is fertilization unnecessary?

The transfer of a cell nucleus from a somatic cell into an enucleated egg cell.

Short Answer is: Creating clones.

Well ... it kills the cell(s) you took the nucleus out of, (you've got to clean out two) But you kill more cells whenever you scratch you head. (by a thousand times)

Somatic cells undergo Mitosis. The nucleus and all its contents have to be replicated (copied) and divided into the daughter cells. The process where the nucleus divides is called karyokinesis