John Piper gives seven reasons that it is important to be part of a Small Group (or Home Group or Life Group or whatever your church calls them) as opposed to simply attending church once a week and hearing a sermon.
1) The impulse to avoid painful growth by disappearing safely into the crowd in corporate worship is very strong.
2) The tendency toward passivity in listening to a sermon is part of our human weakness.
3) Listeners in a big group can more easily evade redemptive crises. If tears well up in your eyes in a small group, wise friends will gently find out why. But in a large gathering, you can just walk away from it.
4) Listeners in a large group tend to neglect efforts of personal application. The sermon may touch a nerve of conviction, but without someone to press in, it can easily be avoided.
5) Opportunity for questions leading to growth is missing. Sermons are not dialogues. Nor should they be. But asking questions is a key to understanding and growth. Small groups are great occasions for this.
6) Accountability for follow-through on good resolves is missing. But if someone knows what you intended to do, the resolve is stronger.
7) Prayer support for a specific need or conviction or resolve goes wanting. O how many blessings we do not have because we are not surrounded by a band of friends who pray for us.
Taken from John Piper’s sermon The Love of Human Praise as the Root of Unbelief