Unlike heterosexual couples, gay and lesbian couples who lack marriage equality are burdened with carrying power of attorney documentation with them at all times to assert their right to make caregiver decisions on behalf of their partners. If someone is rushed to the ER room unconcious, events like a dispute between a partner and a sibling or parents are common and a partner may not have quick and easy access to paper work. Verbal declarations may be impossible because a patient is unconscious, arguments can result and be ugly.
A national database where any couple can register their wishes for a designated caregiver would keep the information easily accessible everywhere in the USA at all times. This would settle caregiver disputes between partners, sibling and parents quickly and avoid ugly escalation and legal battles.
This would relieve LGBT people of the burden of encountering a "papers please" situation and avoid unfortunate incidents like what happened at Research Medical Center in Kansas City, Missouri (one of many states that offers no legal same-sex relationship recognition at all).