The costs of DOMA

As the DOMA wars heat up, it's worth focusing on the costs of DOMA. LGBT elders are severely disadvantaged when their marriages are not recognized. From social security to Medicare to pensions and IRAs, simply being gay, even if legally married, is enough to deprive you of help that a straight couple would have.
From Reuters

Many employment benefits are geared to employee earnings history. But married couples often can take advantage of policies that allow lesser-earning spouses to tap the benefits of the higher-earning partner. That option often isn’t available to LGBT couples – including those who reside in one of the five states (and District of Columbia) that currently have legalized marriage for same sex couples. That’s because the Defense of Marriage Act (DOMA) of 1996 defines the word “spouse” as applying only to different-sex married couples for any purpose involving interpretation of federal law.

My Dad recently died and fortunately my mom will be taken care of. But a gay couple in the same community, even if legally married, will have none of the spousal benefits that my Mom will have.

This is the kind of story that makes it clear that opposition to equality is doing real damage to real people. And for what reason? How does depriving someone spousal benefits "protect marriage"?