OK, this one I can explain. Some photographers have token items that they treasure and want to include in photoshoots. Be it a piece of jewelry, a set piece or even a coat. Most times, when you're working for a client, you can't slip these tokens into the main photoshoot, but if you're comfortable enough with the model you can ask them to make some extra pics. This won't work with any model as most would reject, but almost every model has a main photographer and every photographer has a main model. Imagine you take a selfie with the local newspaper every time you travel, to mark the date. It's kinda the same thing. Photography is not just a job, it's also a passion, so many photographers develop some rituals