In my mind, the USSC isn't 9 "wise people" who carefully consider this side, that side, and the other side, and then Decide. Upon. A. Glorious. Destiny.
What they do is weigh the cases against where the ruling classes want the public to be, and then present it in such a way as to reduce the chance of a revolution being sparked. (See "The Lexus and the Olive Tree" for why I think this)
They listen to the conservative/reactionary side to let them think that they have a chance, that the clock will be turned back to the 1960's, 1950's, or even the 1870's...but it has never happened. Yet the conservatives believe with a great faith that they have a chance to enact discriminatory laws without the USSC objecting...
LGBTQ rights have been a global phenom for quite some time now...all countries are getting on board.