Excerpt from this article:
The reasons why a royal couple might ban social media from their wedding seem fairly obvious: The royals are notoriously private and picky about controlling their images. Better to leave things mysterious than risk an image or post that sends the wrong message getting out. For the average couple walking down the aisle, though, this type of social media policy might come off as a tad draconian. Social media is part of how people enjoy events nowadays, and arguments that it’s shallow or takes people out of the moment feel less compelling with each passing year.
Either way, it seems clear that just asking your guests to refrain won’t do the trick, even when they have the best of intentions. This is where Eugenie and Jack would seem to have gone wrong—either by not actually confiscating smartphones, or by having a dragnet that scofflaw selfie-takers like Bonas could sneak through.