Why can’t the nucleus be considered an obligatory component of the cells of organisms?

The nucleus for the cell is the brain center and the source of genetic information. In the nucleus, all the activity of the cell and its functional duties are programmed. There are simple working cells in the body that simply have to perform their function, without development and reproduction. For example, red blood cells, cells that carry oxygen, are deprived of a nucleus due to the fact that they need more space inside to carry oxygen. They do not reproduce, for them the red bone marrow plays this role.