I will share the main reason why I used to sit in only one place in school and not move at all.
In my school days upto 10th grade, I used to only sit in one place and not move around at all, not even go to toilet. Yes I could control my pèe for about 8 hrs but still not move at all. Thats because in 2013, when I was in 8th grade, one day teacher called me so I had to go out of classroom. But suddenly after I entered classroom,out of nowhere suddenly the boy named Akshith in our class punched my bàlls hard. It really pained badly for me and I sat down and was holding the lower side of my stòmach as it was paining. Other boys were laughing. Thats why I used to not move around because I used to think what if it happens again. Thats why even while fighting my enemy Arjun or any other boy in our class I used to sit and fight only to protect my bàlls from getting punched again. That way Arjun or the other boy used to get an advantage by standing and fighting me hence they could beat me badly.