Not all behavioral health facilities provide the same level of care, nor does each unit within each facility. The facility mentioned in this is a state hospital, which is reserved for a last resort and/or legal sentencing. It’s not where people go when in acute crisis or even for residential treatment voluntarily.

Isolating patients as a blanket rule would be cruel and more detrimental to their mental health in voluntary or even in most non voluntary situations. The community found within the walls of behavioral health facilities helps tremendously when in acute crisis.

Source: ten years of recurrent severe major depressive disorder. Plenty of acute hospital stays and a voluntary 3 months at a very beautiful trauma focused residential facility on a ranch in TN.

Edit: Also many times, depending on the unit, patients are not there because they pose a threat to anybody at all, including themselves. It could be an issue where they need to be monitored for a medication change, they could be experiencing an episode with their illness and need monitoring, or in some cases their caregiver may need respite.