A person who entered an ER with elevated blood sugar levels would be treated with insulin. After the initial crisis was over, they may be given a prescription for insulin. They may not have the money to fill the prescription. They may not have a refrigerator to store the insulin. In any case, after the initial crisis is treated in an emergency room, they will be advised to consult with their family doctor for long term management of the disease. If poor, they will not have a family doctor or the money to consult with one. No one is kicked out of the hospital, but the result of no long term care is obvious.
Call your local ER and ask them how they "treat" long term illnesses of the indigent...I think you will find that they will say: "We are not equipped to do that, we are a critical care unit, maybe there is a free clinic that will do that..." And of course, most of the time there is not.
Homeless people die on the streets every day. Many who live in poverty who are not homeless go home to die. I do not know of any source of data for the cause of each death...neither do you. If you disagree...You prove it is not so.
Diabetes, heart disease, high blood pressure, tuberculosis, emphysema, Lupus, chrones syndrome, etc., etc., etc., are diseases that need continuous maintenance treatment, including education and other considerations that are not provided in a twenty-minute treatment in an ER.