Why was this mental illness and prison necessary in the 19th century?

At the beginning of the 19th century, the treatment of the mentally ill was a distorted reinterpretation of Pinel's moral treatment and used physical and hygienic measures such as: showers, cold baths, whips, rotating machines and bleeds. The cure desired by Pinel was not achieved and these institutions gradually became places of deposit and exclusion, which was considered as a moral disease started to also have an organic conception according to the thought of several Pinel disciples, the treatment techniques used by those who defended organicist theories were the same as those employed by the followers of moral treatment, all with physiological explanations and justifications for their use since then prevail over organicist theories of mental illness resulting from the experimental discoveries of neurophysiology and pathological anatomy.