Wow! You've an inherent ability to completely miss the point of anything, it sadly seems. Please reference again the examples of same billited students or soldiers, and then get back to us all. If you can't (or simply won't) see the obvious potential for excessive and arguably bizzare litigation from legally validating same sex marriages, then you're either being willfully obtuse, or, well...I'll just be kind here and await fruther explanation of your apparent "innocence" of how things work in the real world of courts/lawyers/etc.
Student "A" lives in the same room as student "B" for a year or more. Student "B", since same-sex/etc, now claims a common law "marriage" exists and sues for "divorce" and settlement. Are you at least able to follow that?