Well, I used to think it was a bit naff, but mainly because I'd only ever 'heard' of people doing it, rather than know anyone who did. But then, a couple of years ago, I was invited to one.
The couple had been through possibly the hardest of times I could imagine - she is seriously ill with a condition that will never go away and which threatened her life for a while. It is under control now but could flare up again at any time. It didn't just threaten her life, it briefly tested their marriage (and anyone who says 'well he said for better or for worse, and them's the chances we take') has no idea, none.
The ceremony was beautiful - it was the 2 of them standing there saying to each other, and to their 2 daughters who have been through it all too, 'look, no matter how bad it got, and how bad it might yet become, we never regret what we said in our first ceremony all those years ago and want to say it again'. Not a dry eye in the house. Not to mention the amazing piss-up party after, some of which I cannot remember due to an unfortunate case of glugging wine with every other female present, including the bride, her mother, her sister, and many others tiredness.