Gateway to polygamous marriages
Complicates tax code
Fewer people would marry, meaning fewer children would have the stability of a traditional household
More children will have absent mothers and fathers. Having both is essential.
And many more reasons. But I'm fine with civil partnership in my country tho, because it is apparent that gays never really wanted to get married in the 1st place. It was more of a principle issue for them. As a matter of fact, most would rather have unrestricted polygamous "open" relationships, which violates the very meaning of a civil partnership.
We will continue to keep **** separate, and ya'll will deal.