It keeps fundie types from bitching about Adam and Steve.
How about instead of redefining the word “marriage”, you tell the fundie types to fuck off? Bitches are gonna bitch no matter what you do, anyway.
The fundie types in 21 states enacted constitutional bans on same-sex non-marriage unions.
Inferior unions are meant to sway people who are on the fence about same-sex marriage, not people who are strongly against. Those people aren’t fine with civil unions, and are often not even fine with Lawrence v. Texas. Left to their own devices they will not approve any status other than felon for gay people.