Why might there be “increasing participation by religious organizations in offering substance abuse treatment funded by federal government vouchers”?

Perhaps because, at least in part, “A program’s faith element relates to the people they serve and the type of help they provide, as programs with more explicit and mandatory faith-related elements are likely to be substance-abuse programs.”

Thus, the more explicitly faith-filled substance abuse programs will increasingly face a special temptation to take federal funds for such purposes. And this will lead plaints “that many of the faith-based programs funded by ATR [Access to Recovery] do not meet state licensing requirements, and are permitted to use religiously-based materials in treatment programs.”