We (Catholics) have a variety of theological reasons for maintaining an exclusively male ordained ministry (deacons, priests, bishops). But there's also the practical reason: most of the women who want to be ordained are the very last people who should be in earthly charge of any Christian church. Lesbian, communist, gaia worshipping nuns are bad enough.
I think "most" is too strong, because I know some wonderful women who are great in a pastoral role. But some nuns and other Catholic women seem to have a positive lust to be priests, in particular. If what they really want to do is minister to people's spirits and show them Christ, then they don't have to perform all the offices and rites of the priest to do that. So I think a lot of the women who are so noisily screaming for ordination as priests are merely hungry for power and trying to destroy the dicta and the missions of the Catholic Church as it has existed for two millenia. And yes, it's no coincidence that a lot of them are lesbians and other forms of leftists, nonchristians, abortion supporters, and so forth.
For a long time I'd thought that if I couldn't endure what's been going on in the Episcopal Church I'd become Catholic, because I love the Catholic Church and the hero pope. But now I'm in a splendid nondenominational church filled with joyous people of every conceivable race, ethnic group, and religious background. Christ is preached there and the sermons are so powerful and meaningful that the church is growing at a log rate. This may be the future of religion in America--a polarization between the dying old churches and the energetic, Spirit-breathed new ones.