I'm not sure what you mean by "manualized" but we use Peer Supports (people with mental illness who get a job working at the Community Mental Health agency) doing work with clients i.e. helping with learning to take a bus places, keeping up with medical appointments, accessing resources, and other tasks. I love working with them and having them help our patients.

Well clinician-researchers, if they believe in what they have manualized and have evidence (or are building evidence) on efficacy probably find these approaches help make research more manageable and the assurance of quality in delivery more possible and measurable. For peers, some welcome the structure and like the reassurance of an "approach". Others feel they know better about the issue,... and maybe they do,... and feel restricted by the manual. .. and some also warm up the manual over time.