Keep in mind that the Harris County Jail is, by Sherif Garcia's telling, the largest mental health care provider in the state. Mental illness and/or substance abuse and homelessness run hand in hand, and because of resource constrains on Harris County MHMRA, etc, most of those people are going to end up in jail, rather than a hospital. When they get out, they usually find themselves at the corner of Commerce and San Jacinto. As long as this is the case, there will always be a significant homeless population downtown.