Ok, here's the thing

I believe strongly that people have a natural disposition as to whether they are attracted to people of the opposite sex or people of the same sex. And regardless if a person is heterosexual or homosexual, they should be entitled to unite and spend their lives with the partner that they love. But it's undeniable that in the Bible, marriage is a sacrament that is defined as being between a man and a woman. So my question is...why are gay couples not happy with the categorization of being in a civil union ? You are still under governmental recognition of being united to another person.