As we've seen, the Patterson family seem eager to accept Iris's misinterpretation of Jim's medical condition as gospel. This is, of course, because they, like Iris herself, have given up on him getting better. The deity in the lab coat has told them that his mind is gone and they dare not contradict him. Since they've let themselves believe that nothing can be done, they've left him in the care of an untrained woman who is herself in poor health. This is bad but what makes it worse is that they've taken her promise that she could take care of him herself not at face value when it's obvious that she cannot. We've seen that she only gives Jim what he needs on the rare occasion that it's something she wants for him because she's too stubborn to take the advice of the health care workers because they're younger than she is and are genreally female. Even the Patterson who's there the most has been bludgeoned into accepting the woman's false claims of authority and knowledge. Simply put, April believes Jim is deaf because an ignorant old woman said he is. Having grown up in the Pattermanse, she's unable to look too far beneath the surface no matter how good her intentions are. We know that Jim looks forward to hearing music when April arrives but we also know that Iris has taken her aside and told her a bunch of codswallop about his having gone deaf based primarily on his not listening to an old windbag who doesn't have the patience or brains to figure out what he wants. Therefore, April dutifully drinks the Kool-Aid and lets Iris screw up.