I know people who've married for several reasons eg
-all their friends were doing it
-they wanted kids and felt that they should be married first
-pressure from parents
-they wanted to move in together but wouldn't without marrying
-so that parents aren't still next of kin
-they were already pregnant or had kids and wanted to 'legitimise' them
-that they felt they were getting old and if they didn't take the plunge they'd miss their chance
I'm not belittling these reasons but it does make the romantic side of me a little sad that just being overwhelmingly in love with someone else hasn't been the reason for marrying I've heard from anyone recently.