They have been forbidden from doing so by people that fear that the institution of marriage is threatened. I’m not sure how it can be more threatened, with 50% of marriages ending in divorce, politicians afraid to express their sexuality except for airport restrooms with complete strangers and the amount of infidelity that exists in the modern American marriage.
To those brave souls that are taking the plunge in California, I say congratulations. And you are living, loving proof that love will conquer hate every time.