Why don't cells continue to grow as an organism grows larger

Body cells don't live long. They only live a couple of weeks or months. The only thing is that white blood cells live a lot longer than red blood cells. They don't grow larger because cells are microscopic. They have to be able to fit through arteries and veins in the body. There must be enough to supply oxygen towards the organs in the body. Cells are made in the bone marrow and are produced in the same size. Unless you have a disease like sickle cell anemia, your cells are round, small, and microscopic.