Hi KingCrimson,
I think God, being the Creator, defines what is male. He made man's physical being, and while we see maleness only in physcial gender, it is so much more in role and position. He made men and women to be one flesh, but the man is, in the marriage picture, related to God and Christ. Father and Son are pictures here, before us, of who Father God, and Jesus the Son are in relationship to each other. Father and child are who we are in relationship to God the Father, and brother and sisters to Jesus, our brother. So, He defines us, it's not the other way around...we, our earthly relationships, are merely pictures of Him in this sense.
Woman are always related to the Church, who is the Bride, and who has a submissive and distinctly feminine role as the weaker vessel, and in need of a husband's, or father's, care and protection and headship always. (Think before feminism hit the scene so hard. :wink: ) She will also be joined with God, in a 'one flesh' sense soon.
God is male, because this is how He reveals Himself, and as Creator He holds the definition, not us. He is the pattern, and we are the copy. He give us a picture of His Authority, His Headship, His Protection, His Provision, His Knowledge and Wisdom, etc. I would say those attributes of Himself, that He has taken and applied to the position of Husband and Father here, are male. He even compares Himself to man in the way of intimate relations in Song of Solomon. We have a dimmer view of these things in these modern times, with the feminizing of men being so rampant.
I will say, though, that there is a completeness to God that is beyond us. We need a marriage to be one flesh, and even then we are still in need of God. Anyway, woman, is simply man with a womb, but God even uses an attribute of women in a sense. God is El Shaddi. El means Power, or Strength, and Shad actually means breasted one. El Shadai means All Sufficient One. God is able to provide us with all, much like a mother is able to provide a baby with all the nourishment it needs for awhile. Obviously God's power goes far beyond a mother's, and so I see this again as a display of His power and care, not really anything feminine, but certainly loving and nuturing. Jesus also speaks to Jerusalem about gathering her like a hen does her chicks. So, this again is the care mixed with the protection...hidden in Him, much like the church is hidden in Christ, and the wife hidden in the husband. Woman being made for man, and glorifying her husband, the church being made for Christ, and glorifying Him. Men and women are both in His image, but the role and position of men here is a partial picture of who God is to us, as His children and as His church. Like I said, it's hard because we have distorted so many of the pictures these days.
I hope this helps some, and I am sure there are probably better reasons than this, but this is the one I know of.