it's a romantic thing.
just revisiting that wonderful day and reaffirming what you have. things haven't gone sour for my hubby and i but we're thinking of running to vegas and getting married again. just to be spontaneous and romantic. also, a lot of times people renew their vows because the first wedding wasn't really a wedding at all. people all the time will have a civil marriage in court and then when they save up money, will do something more fancy.