Having both sexes involved keeps things balanced. Since women are legitimate thinking, breathing adults whose opinions matter because they are just as much a part of the human race, then why shouldn't they be able to get involved? If only men are involved, that basically puts men in total control--a phenomenon we don't want because it could lead to our voice not being heard.
Women should enter politics because the decisions made by members of politics effect everyone. A man making decisions may not always consider everyone in their solutions, whereas if women help more positions, that chance could sufficiently be lowered. Women and men are equal in the sense that it shouldn't be mostly men in this force or field.