One of the reasons might be transportation. In third world countries, where most people have little money, transportation is an issue.
in our assignment, in our congregation, we had only five or six families with old cars. On Tuesday nights, after the ts and service meeting some of them had to make three or more trips from the hall to surrounding villages, sometimes untill 11:00 PM, to take friends home. So as soon as possible we tried to establish groups and later small congregations in those villages. Problem was the lack of capable brothers.