Why can't gay people get married just because someone else thinks it's immoral to THEIR OWN religion?

Its not just a religious thing, I know a lot pf people who aren't religious believe that marriage was only intended for one man and one woman! If it was only because of religious views it would be ped in more states because a lot of people aren't. . .I personally have nothing against it, I feel like it wouldnt be something that would hurt anyone, and ever person should have equal rights! Your right though about the whole idea of marriage being sacred and that most of them end up in divorce anyway!! So I don't understand why people use that excuse!