The provision of housing to the homeless can be refused for a lot of reasons. One being that the housing might be in a place where the person has no access or restricted access to other social programs such as food or jobs programs. The housing might make them feel unsafe, such as being crammed into a shelter. The housing might be overly restrictive, such as refusing to allow them to bring their pet which may be the only thing keeping them going emotionally. They may feel they don't have adequate support to transition to housing, if the housing demands they get off an addictive substance first (chicken and egg problem, because its much harder to get off an addiction if one is currently in crisis like being homeless).