Why are personal budgets not used more in mental health?

People with mental health problems are less likely than other eligible groups to use personal budgets, which give them direct control over selecting and paying for their own support. But when they do have them, the money is spent in imaginative ways. People tend to select things like gym sessions to manage their health, IT to build social networks and sleep-in support to alleviate mental health problems like paranoia. So why has personalisation not really taken off in mental health?