I agree with miamifella - there are lots of AA/NA meetings to match clients up with, but not many other groups.
In the detox center that I habitually attended, people from AA, NA and CA came in to chair meetings several times a week. The counselors loved this because it provided free baby sitting - the clients were kept entertained for an hour (or more) at a time, and the counselors were freed up to catch up on paperwork, or whatever else they did while not dealing directly with clients.
Also, AA volunteers took clients out to meetings in the community most evenings. Most clients loved this because it gave them a chance to smoke (>99% of the clients were smokers, and smoking was banned in the whole detox property). The bad news was that some clients smuggled cigs back into the detox building after going out to AA meetings, and many were subsequently thrown out for smoking surreptitiously in the building. This didn't attract me because I have never smoked.
The relationship between the detox establishment and AA was mutually beneficial - the counselors got a bit of free time, the clients got to smoke once a day, and the AA groups had a captive audience to practice step 12 (spreading the word) plus a steady stream of new recruits. So it is not surprising that the counselors pushed the AA message.