Because of the lack of nuclei and organelles, mature red blood cells do not contain DNA and cannot synthesize any RNA, and consequently cannot divide and have limited repair capabilities.
The inability to carry out protein synthesis means that no virus can evolve to target mammalian red blood cells.
It simply allows the red blood cell to have more hemoglobin. The more hemoglobin you have, the more oxygen molecules you can carry. Therefore, it allows RBC to transfer more oxygen.
Lack of nucleus in RBC also allows the cell to have an unique bi concave shape that helps with diffusion
