Why is it legal in some states to marry the same sex?

Answer 1

The culture is some states is more liberal than in others and in those more liberal states the citizens do not try to control what people do in their private lives. They are more accepting of people who may be different or have different perspectives. Also, religious sects do not have such a strong hold over politics in those more liberal states and religious groups are the number one foes of laws that protect gays.

Answer 2

Utah had a provision it its state constitution and a state law prohibiting same-sex marriage. However, on December 20, 2013, a judge in the federal district court ruled that both of these were unconstitutional and struck them down. When asked for a "stay," a temporary delay in implementing the decision while an appeal is decided, the judge refused. Therefore, same-sex couples were able to marry immediately.

On June 25, 2014, the 10th Circuit ruled that Utah's ban on same-sex marriage is unconstitutional. This ruling is binding also on Colorado, Kansas, Oklahoma, New Mexico and Wyoming. The decision, however, was temporarily stayed (delayed) for at least 90 days pending appeal. That stay was lifted on October 6, 2014, when the United States Supreme Court refused to hear the appeal and let the 10th Circuit's ruling stand.