Married couples have constitutional and legal protection. Civil partnerships have legal protection only. Legal protection can be changed, amended, whittled down by act of the Oireachtas. Constitutional protection can only be removed by a vote of the people in a referendum.
It is a myth that surrogacy and the marriage referendum are connected. The right of a married couple to procreate does not, and has never been defined to, include a right of access to artificial means such as surrogacy.