Even in the Old Testament he compares his relationship with Israel as a husband-himself- and wife-Israel. Why he does this, I don’t know. Apparently symbolism is important to God.
God didn’t do this. The way most of the writers of the Bible chose to convey the image was God=male church=female. God did not choose this. I guess the males(who were the writers back then) liked the idea of the male having all the power and again, a reason to mistreat females. But doesn’t it say that God is beyond humans, unimaginable to them? I think that God may have used a male image to make him/her easier to understand. God isn’t really even a person. No human concept can describe him/her, so in conclusion there is no reason not to let females serve other than wrotten tradition. And again, what is right is not always popular. What is popular is not always right.