Its a memory captured forever, in its own little flat object, that can be torn with the slightest touch.
Sometimes its all we have left of a previous adventure or maybe the night that no one remembers.
Humans need to treasure these moments for as long as they can, some might not want to because of reasons, others might not be able to control what they forget.
Memories will fade and turn into nothing, photos will fade too, but they go black and white and stay forever.