Thus, they are missing out on the Sacrament of Matrimony and the graces included.
Most still get a preacher to preside, but they have to find one willing to do it at a venue that is not their church.
Any priest or preacher who will only conduct a wedding ceremony in their own church will have seen the number of weddings they officiate go down rather dramatically as the price they charge has gone from zero to thousands.
In the protestant churches they aren’t missing anything spiritual by not marrying in a church house. In Catholics possibly so?
But just as worship can be done on the hood of a jeep, a wedding can be anywhere that people gather in his name.
One of the most amazing easter services I ever attended was in Moab Utah, in the back country, with friends standing around a few jeeps. Nobody even passed the plate and put the bite on us.