Because gays not being able to marry is an injustice, an unfairness, oppression, etc. Priority #1 is to stop doing harm to those people however it can be implemented. We didn't* say "Oh black people should have rights, but let's postpone that until we can come up with the best possible way to write it in legislature"
*racist people did in fact use that argument
Yes we did. Black people were legally discriminated against for almost 100 years until the Civil Rights Act. And before that, we were slaves until the 14th Amendment. Similarly, women weren't allowed to vote until the 19th Amendment.
I'm all for civil disobedience in the face of injustice. And I'm 100% for gay rights. And I'm ecstatic about the court's decision today. I think it was undeniably right from a moral perspective. But it was probably wrong from a legal perspective, and that's worrisome.