They didn't draw the line there, that's case that was brought forth. That's how the courts work.
That's not how the Supreme Court works. They are selective about the cases they hear. Especially looking at a 6-3 ruling with this court it's clear to see this was an ideological selection.
Given that, it really does seem that the court ruled 6-3 in favor of the plaintiffs who are trying to draw a line around gay couples because the court is trying to draw a line around gay couples.