Some cells in our body have lost their nuclei, so what function has become impracticable?

Some cells in our body have lost their nucleus. For example, erythrocytes. They have lost the core because it takes up a lot of space. As a result, new red blood cells can carry more oxygen by simplifying their structure. But they also lost the ability to divide. The nucleus is responsible for storing genetic information and division. Still, new cells can form in the red bone marrow. Some other species have nuclei in red blood cells. Therefore, they can divide without the participation of special organs of the body.