What you say about churches being welcoming agrees with my experiences too, from what I've seen of others, given that I don't attend. But I think faith is only part of the reason for attending.

Essential in the choice to join a church is the desire to seek out a kind of 'marriage', where for better and worse, you promise to look out for others in an extended family and to help them when they need you. That sense of belonging is one of the big things that brings everyone in a church together -- the wish to be part of a community that regularly joins together and where you can share your life with others.

Membership in a social club can't do that.