I found the above graphic on a random church's website. The clear implication is that their church needs small groups in order to do life together because "We can't do life alone." Another (I'm sure unintended) implication is that their other church activities do not involve doing life together.
It is a sad thing that so many churches in our country feel the need for small groups. The reality is that small groups shouldn't have to exist. When a church gathers, mutual edification and fellowship should automatically occur. However, churches that express the need for small groups are admitting - albeit inadvertently - that their worship services, for example, do not foster community.
When any church comes together, it ought to feel like a family gathering. Assuming that you had a nice Thanksgiving Day with family, that is how a church get together should be. You hang out, talk a lot, eat a bunch, discuss life, and maybe even watch some football (especially if an awesome team like my Buffalo Bills is playing). Christ's body comes together for the very purpose of the mutual upbuilding of the body.
In the context of church gatherings, the Apostle Paul writes, "What then, brothers? When you come together, each one has a hymn, a lesson, a revelation, a tongue, or an interpretation. Let all things be done for building up" (I Cor. 14:26).
Paul also says the following, "Rather, speaking the truth in love, we are to grow up in every way into him who is the head, into Christ, from whom the whole body, joined and held together by every joint with which it is equipped, when each part is working properly, makes the body grow so that it builds itself up in love" (Eph. 4:15-16).
Mutual edification is not some by-product of church meetings. It is the primary purpose of those meetings!
Small groups should not be needed because every church activity ought to be doing life together. That's how mutual edification occurs. If that's not happening, then those other activities should be quickly jettisoned.
Large churches embrace small groups (or "Life Groups" or whatever else they are called these days) because their large worship service/ceremonies do not bring about mutual edification. It's that simple.
When we follow the pattern for church life that God has given to us in the Bible, then there's no need for small groups. This is because the small setting, with meetings ideally occurring in homes, naturally leads to mutual edification and healthy body life.