Gay or straight, love is not always permanent. Couples, married or not, go their separate ways. It may be that you flew to Boston with the love of your life in May of 2004. You got married to celebrate the new available legal marriage status for same sex partners. That was years ago. Your love didn’t last a lifetime and you’ve long gone your separate ways.
The Boston marriage is a distant memory that you remember fondly as a whirlwind of sightseeing, seafood, and romance. But otherwise you never think of it – you’re single now.
You may be living as a single (or as a cope with someone new) but for tax purposes you are still married to the old love of your life unless you’ve somehow managed to get legally divorced.