I’m surprised they are still a thing of weddings now that everyone has smartphones. Maybe they are considered nostalgic for the period before smartphones and digital cameras. Or maybe there is no good way to share photos from guests.
I think the bride/groom buy a bunch and hand them out. You're supposed to put them back when you're done and then they will have the photos all aggregated and publish them online. Tends to lead to better candid moments for the wedding. At least that's what happened at a couple of weddings I went to.
