One of the cases that prompted the [Obama administration's Defense of Marriage Act] shift was filed by Edith Windsor, who sued after the federal government refused to recognize her 2007 marriage to her partner, Thea Spyer. After Ms. Spyer's death, Ms. Windsor faced a $350,000 estate tax on her inheritance from her partner, a tax she wouldn't have incurred had her marriage been recognized by the federal government.
Because US history is to a large degree the story of very wealthy people asserting their rights as a group -- leaving everyone else to play catch up -- any attempt to discriminate against groups that include very wealthy people are often frustrated until that group can be reconstituted along class lines.
In the case of gay marriage, the stigma attached to homosexuality has until only recently proven itself superior to the appeals of upper class gays to take their rightful place amongst their wealthy counterparts -- to marry whomever they want.
If US history is any guide, we can expect that what is likely gained by all gays in the realm of marriage will not translate so well to other spheres, like health services, which can be delineated much more easily by the criteria of class. In other words, in the case of marriage, it will be hard to deny to poor people this right that is increasingly seen as inalienable for the rich -- but others will remain out of reach.