Here are just a few of the reasons: from House Church Central web site (see link to the right)
Historical. The house church is the biblical church. All of the churches in the New Testament era were small assemblies that met in homes. While setting up institutional forms of “church” may or may not provide a way to honor God, the movement toward the institution and the human authority that tends to accompany hierarchical institutional structure are not theologically neutral.
Growth. The most explosive growth of Christianity in our own time has taken place in the likes of the People’s Republic of China where its only expression has been the illegal, underground house church (more recently the PRC has installed a government-licensed “Three Self” church in an effort to control a movement that decades of political repression has failed to contain). Historian Del Birkey’s studies have led him to conclude that the house church is our best hope for the renewal in our times.
Resisting the Culture. Our culture desperately wants to change our doctrines so that it might make over Christianity to conform to its notion of “civil religion” and “political correctness.” The house church has always been counter-culture for this reason, just as Jesus said that his disciples should be in the Sermon on the Mount. That sermon outlines how the powerless disciple can be salt and light in a dark world (Mt. 5:13-14), how to withstand evildoers (Mt. 5:39) by showing God’s love to the world through suffering at the hands of persecution from bullies (Mt. 5:39), foreclosing landlords (Mt. 5:40), and occupying Roman authorities (Mt. 5:41). It speaks of giving and lending to the most hopeless credit risks (Mt. 5:42). It speaks of a praying community (”Our Father, who art in heaven …” Mt. 6:9) that fasts (Mt. 6:16), gives of itself (Mt. 6: 21), and depends completely on God (Mt. 25ff). It speaks of the non-judgment of individuals (Mt. 7:1), just as it speaks of the need to judge those who would be authorities in spiritual matters (Mt. 7:15ff).
Mission. There are several opportunities in our communities that are especially suited for the house church. An invitation offered to a work-place acquaintance to a home is much less threatening than one to a church, just as one example. Another is the unique value of the house church as a ministry to “the damaged” and the possibility of learning the joy of giving by elevating that practice to a personal level.