At the most basic level, and at every point thereafter, marriage is distinct from ss couples.First Circuit Court of Appeals:
"Although the House Report is filled with encomia to heterosexual marriage, DOMA does not increase benefits to opposite-sex couples--whose marriages may in any event be childless, unstable or both--or explain how denying benefits to same-sex couples will reinforce heterosexual marriage. Certainly, the denial will not affect the gender choices of those seeking marriage. This is not merely a matter of poor fit of remedy to perceived problem, Lee Optical, 348 U.S. at 487-88; City of Cleburne, 473 U.S. at 446-50, but a lack of any demonstrated connection between DOMA's treatment of same-sex couples and its asserted goal of strengthening the bonds and benefits to society of heterosexual marriage."
From start to finish, and in the end, ss couples will only ever be a mutually sterile, pointlessly duplicate gendered half of marriage.