I've addressed Range of Motion (ROM) for people in bed. The video specifically talks about the wheelchair.
I have recommended ROM exercises to immobile people. In the video, the woman and her caregiver/husband show how.
ROM exercises are done to keep the joint in working order. If some sort of cure is found in the future, the person with the disability will want to be able to use those joints again. This will not be possible if the joint ends up frozen, deformed, or in some other way to not be working properly.
For a growing child, it is very important to do these daily and to wear braces and splints as directed. The reason is that bones and joints grow. A spasmed muscle can pull on a growing bone. Deformities can form. (Make sure to always check braces and splints for proper working order and if it is causing any redness or chafing.)
Children grow. They need to wear
(This doesn't say, but appears to have been a fracture.)
Now this is a personal experience.... At a long-term care in a hospital, there was an older woman who was Spanish only. She did not speak, but followed simple commands in Spanish from her husband. Maybe she had had a stroke. She used a wheel chair. She had developed a habit of wrapping a foot around a wheel chair leg. It looked odd and her foot was becoming odd-looking.
One day the Physical Therapist came to observe her. She ended up getting passed over for a walking rehab program. The reason was her foot.