There could be psychological factors. A very traumatic event, like a major accident or the loss of a loved one, might cause the 13 - year - old to regress in some ways, including bladder control. They might subconsciously go back to a more infantile state as a form of coping mechanism.
One possible story could be that the 13 - year - old has a medical condition like incontinence. Maybe they had an accident that damaged their bladder control, and so they had to go back to diapers. It's a difficult situation for the child, having to deal with this change at such an age, and they might face a lot of embarrassment and challenges at school or among friends.
It is extremely uncommon. At 16, people are generally expected to have mastered toileting skills. However, there are exceptions like if there are underlying health problems or very unusual circumstances such as a severe accident that affects the body's normal functions.
She could be a very active girl in sports. During intense training or competitions, she sometimes has little accidents due to not being able to get to the toilet in time. So, she starts thinking about using diapers to avoid such embarrassing situations. For instance, during a long track and field meet, she had to hold it in for so long that she almost wet herself. That's when the idea of diapers became more appealing to her.
No, it's not very common in the general population. ABDL is a niche interest. Most 21 - year - olds are focused on typical adult things like education, career, and social life. But within the ABDL community, there are individuals who may explore this at that age.
I'm not sure what specific story you are referring to. It could be about a 15 - year - old who has a medical condition that requires the use of diapers. Maybe it's a personal and difficult situation for that individual, like having incontinence due to a physical disorder.
Perhaps she is on a long camping or hiking trip with her school group. There are no proper toilet facilities around, and she realizes that having diapers would be a practical solution. She might be too shy to tell anyone at first, but then she confides in her best friend from the trip, who then helps her figure out how to manage the situation.
It could be that the 15 - year - old has an accident - prone nature and has to use diapers for a short period of time, like if they have just recovered from an injury that affects their bladder control.
One reason could be a medical condition like a bladder disorder. This would mean that the 15 - year - old has no control over their bladder and needs to use diapers. Another could be a neurological problem that affects the body's normal functions related to bladder control.
We should focus on positive and healthy aspects of an 11 - year - old's development, such as their school achievements, hobbies and friendships, rather than such embarrassing and inappropriate topics.