Intimate surroundings promote closeness. There is no better place to get to know someone than in the setting of someone's home. Finally, to promote and maintain fellowship you need a focus for the meeting. When we center our time together around God's Word, in His presence we can take off our masks and reveal ourselves without fear of embarrassment. Meeting once a week during the Sunday service alone won't do it because we show so little of ourselves in large groups.
Fellowship is promoted by the closeness of the home Bible study.
And they continued steadfastly in the apostles' doctrine and fellowship, and in breaking of bread, and in prayers. And they, continuing daily with one accord in the temple, and breaking bread from house to house, did eat their meat with gladness and singleness of heart, Praising God, and having favor with all the people. And the Lord added to the church daily such as should be saved. Fellowship revolved around both the public meetings and small gatherings in individual houses. Home fellowship was a much larger part of the early church because there was no rapid transportation.