Nitpick: except red blood cells. White cells very much do have mitochondria. RBC's don't need them because they are incredibly low-metabolism. It's energetical

Nitpick: except red blood cells. White cells very much do have mitochondria. RBC's don't need them because they are incredibly low-metabolism. It's energetically cheaper for the organism just to make them, let them go for a few months, and then recycle the components.