As someone who is an adult and wets the bed occasionally , I think I may know an answer . It has to do with hormones and development . When your bladder gets full , meaning where you can pee , it sends a signal to the brain which let ' s you know you have to go . If you are asleep , the signal will wake you up . For children the brain is still developing and the body ' s systems are still being tuned , so the signal doesn ' t always emit or get received . When I went through basic training in 2014 I had a pocket stress fracture in my hip directly on top of that one huge nerve in your hip on the right side , the cyatic ? Syatic ? Anyway , the fracture healed but the nerve is now being squeezed by the new bone so my hip is constantly in pain , to counter this pain my adrenal glands are running overtime so I don ' t always receive the signal my bladder sends to my brain . Sorry for the semi long response and personal anecdote . Hope this helps !