No society should change the definition of a bedrock institution such as marriage without a damned good reason. pandering to a minority of a tiny minority is not a good enough reason.
The last time the left tampered with the institution of marriage in the name of "fairness" and "compassion", we got "no-fault" divorce. Since that date the number of divorces has risen astronomically and the number of people getting married has shrunk.
Marriage is not a good deal for men these days since a woman can repudiate the marriage contract at any time for any reason and soak the man with alimony and child support for years. This is what the left has wrought with the last definitional change. Why should we change the definition again?