OK, I'm going to take my courage in both hands and post in FWR for the first time, don't squash me please...
Just in case you want a slightly different starting point and perspective, HullyDS.
The biblical view that the various (bible believing) churches I've been part of have always taught and I've studied is that humanity was created male and female to be in perfect harmony together. 'The fall' when they chose to disobey the one command God had given was both an undermining of this perfect harmony in the incident itself (Adam promptly blames Eve for 'making him' eat as soon as God comes looking for them, she blames the serpent even though people were given stewardship of the animals etc) and then it was a part of the judgement God made that relationships between men and women became selfish and conflicting. So the 'battle of the sexes' in Genesis 3:16 terms is "Your desire will be for your husband, and he will rule over you."
I realise that quoting the bible as if we should actually pay any attention to it is rather inviting ridicule here, but hey ho. And you're 14, so it can't hurt to know that some people (rather a lot of thoughtful, intelligent people I know too) think otherwise.
Anyway, so in a nutshell, the biblical answer to your question would be, because the general human condition that we now endure is for women to seek domination and control over men and for men to seek rule and power over women. As a few people have noted, human history does involve examples where each side has been the more 'successful' although western history largely shows male 'success'.
And yes, 'religion' and its institutions have been fully involved and instrumental in encouraging such subjugation, including christian structures, particularly of women. But that's just because christians are still flawed and fallen human beings, just knowing we're forgiven and awaiting a redeemed and perfect world when we will no longer have to endure such a condition.
OK, that's it. And please, this is just a contribution, not an invitation for jeering.