The question was simple
Can someone give me their reasons for officially becoming a member of a church?
I have a lot of thoughts (and interesting stories), but thought I'd share my brief reply:
Same reason I had a marriage ceremony and have a certificate. God didn't need that. My wife didn't need that. But, the outward expression and "hoops" we jump through are human bolsters to something spiritual God does.
In Membership I have placed myself under authority and accountability in a human way which gives testament to a spiritual reality of entrance into a local church's community. It isn't necessary, but extremely helpful.
As a pastor, it is 1000x easier to work with someone having an affair, gambling addiction, or other life issues if they are a member who has "officially" placed themselves in a position that is open to church discipline (such as being removed from a leadership role) than someone who is deeply committed, but just "doesn't see the value"
I feel similar to the way people live with their "fiancée" for 10 years and never really bother getting around to the marriage part.
The New Testament calls us to accountability with one another and even prescribes removing leaders and people from positions or the community itself if necessary. It is very difficult to "remove someone" from the community if there are no boundaries of what the community is (an active membership roster).
In our denomination, everyone is required to reaffirm their membership every year, continually testifying that they are in it together, to pursue God in a unified and likeminded way. We don't want ancient Membership lists of 400 people when 125 show up for worship. We want a living, breathing, committed, unified force of God willing to submit to one another.