Because marriage is a state matter, there are no nationwide records on how many couples get religious ceremonies with the weddings, but an article in USA Today indicates that the numbers of purely civil weddings are on the rise:
14 [states] showed a growing or essentially steady rate of civil marriages — more than 40% of marriages in 2001. That’s up from about 30% in 1980.
Four [states] showed a drop in civil-marriage rates: South Carolina, where a legal change stopped judges from getting paid for weddings (but the state still has one of the highest civil-marriage rates); Utah, with its large, family-centered Mormon population; and tourism havens Hawaii and Tennessee, where visitors flock to be quickly wed by non-denominational ministers.
Why are more people choosing to go with some sort of civil marriage ceremony rather than the traditional, religious ceremony in a church or other house of worship? One factor may be the rise in interfaith marriages. Another is surely the dropping numbers of people who are affiliated with churches — most churches will only marry a couple if at least one of them is a member of the congregation. Finally, the increasing numbers of people who are uninterested in religion is likely playing a role as well.
As the religious aspects of even the wedding ceremony, never mind marriages themselves, continue to decline, it will be more and more difficult for conservative religious leaders to assert “ownership” over the nature and definition of marriage, something they do as part of their effort to thwart the legalization of gay marriage.