I think this is a strange and very modern conception of weddings. Weddings are not just about the bride and groom; they're about the bride and groom and the community of their friends and family. That third part is a key component! It's why we invite people to weddings, so they can witness and help the couple in making and keeping the commitment of marriage.
True, of course, but they're the ones spending a fortune on it. Not only so they can have a memorable day but so their guests enjoy it too. Seems fair that if they ask you to do something really really easy like not take photos, you do that.
