The answer, according to some Christians, is that God designed and created women in order to manifest beauty. According to John and Stasi Eldredge,
She is the crescendo, the final, astonishing work of God. Woman.
In one last flourish creation comes to a finish not with Adam,
but with Eve... Given the way creation unfolds, how it builds to
ever higher and higher works of art, can there be any doubt that
Eve is the crown of creation? Not an afterthought. Not a nice
addition like an ornament on a tree. She is God's final touch, his
piece de resistance... Look out across the earth and say to yourselves,
'The whole, vast world is incomplete without me. Creation reached its zenith in me...There is something uniquely magnificent and powerful about a woman. We tried to reveal the immeasurable dignity, the holiness of your feminine heart by showing that it is God who longs for Romance...it is God who reveals beauty as essential to life. You are the image bearer of this God. That is why you long for those things too. There is a radiance hidden in your heart that the world desperately needs...she is captivating, uniquely glorious, and he cannot be. She is the incarnation of the Beauty of God. More than anything else in all creation, she embodies the glory of God. She allures the world to God.
-- selected quotes from Captivating: Unveiling the Mystery of a Woman's Soul
In other words, God designed The Woman to reflect his image and likeness in a unique way, to make known and reveal the Beauty of God. Women are beautiful because God is beautiful.
As wonderful and empowering as this might sound, not all agree with proposal. Of course, some without faith in the Christian God might simply suggest that the attractiveness of women has something to do with biological evolution. But beauty transcends sexual attraction, and in my mind is something entirely else. However other Christians have critiqued this beauty theology. For example Shawna R. B. Atteberry, a pastor and writer, blogs thus:
We live in a society that idolatrizes its version of beauty to the extent that girls and women suffer from various eating disorders in order to try to be “beautiful.” I do not believe this is the advice Christian authors should be giving to their readers...this is a finicky femininity. I also think it is a dangerous one. The church should be giving a different view of beauty, and what makes a woman beautiful. Although they encourage women not to listen to the culture, it sound like in the end the Eldredge's buy into culture’s definition of “beauty.”
-- blog post: What is Beauty?
Whilst Shawna has a point, I do wonder if she is throwing the baby our with the proverbial bathwater. Yes, as I recently blogged, young girls do suffer eating disorders, but this is because they are trying to lose weight. Here we see a rhetorical slight-of-hand. The Eldredge's said nothing about skinny girls. On the contrary, if young girls could learn that they are beautiful in God's eyes, and they are to display his beauty and celebrate their femininity, that would surely prevent all this weight-loss nonsense. You see, the problem with the contemporary culture is not that it teaches girls that they should be beautiful, but that it constantly tells them that they are not beautiful yet, because they are too fat one minute and too skinny the next. It also prescribes a very narrow vision of what physical feminine beauty is.
Therefore, for the avoidance of doubt, let me say what I believe: God created all women to be beautiful and to radiate His glory, in body, mind, soul, character, personality, and spirit. This has nothing to with physical preferences (short, tall, skinny, slim, curvy, fat, blonde, brunette, whatever!).
There's so much more to say on this topic but I think I've said enough for now. Perhaps my readers can keep the debate going.