Why does meiosis produce four sperm cells but only one ovum?

Both meiotic processes produce four cells, but, in the case of oogenesis, only one of those cells becomes a mature ovum, due to unequal cell division. It's important that the ovum has a large amount of cytoplasm and all the organelles for the potential zygote. The sperm cells carry only genetic material, so there's enough cellular material for all 4 of those to mature...