Whether or not you favor marriage as a social institution, there's no denying that it confers many rights, protections, and benefits--both legal and practical. Some of these vary from state to state, but the list typically includes:
Suing a third person for wrongful death of your spouse and loss of consortium (loss of intimacy).
Suing a third person for offenses that interfere with the success of your marriage, such as alienation of affection and criminal conversation (these laws are available in only a few states).
Claiming the marital communications privilege, which means a court can't force you to disclose the contents of confidential communications made between you and your spouse during your marriage.
Receiving crime victims' recovery benefits if your spouse is the victim of a crime.
Obtaining immigration and residency benefits for noncitizen spouse.
Visiting rights in jails and other places where visitors are restricted to immediate family.
Same-Sex Marriage, Civil Unions, and Domestic Partnerships
On June 26, 2015, the U.S. Supreme Court decided the historic Obergefell case and ruled that same-sex marriage bans are unconstitutional, and same-sex couples can legally marry anywhere in the United States. If you are in a same-sex marriage, your unioin will be legally recognized everywhere in the United States, and you are entitled to all of the same state and federal benefits as opposite-sex married couples.
However, these rules do not apply to unmarried couples that have established either a domestic partnership or civil union. If you are in either of these two marriage-alternative unions, none of the benefits of marriage under federal law will apply to you, because the federal government does not recognize these same-sex relationships. For example, you may not file joint federal income tax returns with your partner, even if your state allows you to file your state tax returns jointly. And other federal benefits, such as Social Security death benefits and COBRA continuation insurance coverage, may not apply.