We all remember a scene from a television show or book when a character just happens to have an important item necessary to solve a problem in his or her pocket, don’t we? The Doctor with his sonic screwdriver or psychic paper or strange bit of metal that he happened to pick up along the way. No, wait, that was MacGyver that spent the first part of the show picking up odd bits of things that he would later pull out of his pack and assemble into something. Batman may not have pockets, but he sure manages to carry quite a number of useful items in his utility belt.
A character in a Middle Grade story could have any or all of those items in his or her pockets. Maybe an item might be important to the story or they could be just interesting indicators of the character's personality. If this was a YA story, something in the character’s pockets (if mentioned at all in the story) would have to be important in some way. Otherwise the contents of the pockets (or purse or backpack) won’t be mentioned at all. Since time is limited, a television program might only have a brief glimpse of stuff, but only an important item would be shown in focus.
One major complaint I have about women’s clothing (and girls’) is the lack of pockets. Of course women don’t need pockets, the fashion industry insists, they carry purses. Pockets are important. My work clothes had to have pockets and I heavily used my jacket pockets (for keys, sticky notes, pens, flash drive and tissues, all necessary in my job). Maybe the need for pockets is why lab coats are so popular among mad scientists.
Harry Potter is lucky enough to be set in a time where wizard/school robes have pockets that can hold a wand and other items. My wizards carry a lot of pouches on their belts with magical ingredients.
What stories have you come across where pockets or the contents of them turn out to be important? And yes, that also includes purses and backpacks.