1) hard to find locations in private homes or schedule them at the KH when 2 or more congregations share one building.
2) hard to find "qualiified" conductors, MS (readers), etc. In this area there are fairly enough elders but only 1 or 2 MS per congregation.
3) and as sir82 said, smaller book studies can be a platform for the conductor's private interpretations
Blondie