Why aren't all the cells in our body totipotent our entire lives

somatic cells have highly specific functions

Explanation:

In our body, the major part of cells is irreversibly differentiated into somatic cells. From a cellular point of view, this process of differentiation seems to be an evolutionary disadvantage. However, cellular differentiation is a process aimed at exploiting the genetic variation in order to obtain a highly specialized cell type that is capable of carrying out a specific cellular function. For example, keratinocytes are highly specialized epithelial cells that function by separating the organism from the surrounding environment.