I saw a lot of this exact behaviour in Ibiza recently, I will never understand it. I use the iOS photos widget to always have a photo from my camera roll on my home screen, and the little moment of joy I get from that is usually the memory of the event depicted. What future joy is going to come from a photo popping into your day of that time you spent 2 hours standing in front of something doing very slightly different poses while your long-suffering friend or partner was forced to take photos of each and every one of them?