Because he's got nowhere else to go?
Because being a ........ is as close as he gets to having a personality?
Because he's chained to the wall in his basement and covered with excrement - which just makes him naturally morose.
Because he's fantastically insecure and he repulses people before they can reject him?
Because when his morning shot of steroids kick in he forgets to take his daily dose of Aripiprazole, Asenapine, Cariprazine, Clozapine, Lurasidone, Colanzapine, Quetiapine, Risperidone and Thorazine?
You sure figured it all out, Dr. Phil!