The Myers/Briggs/David Keirsey folks identify four primary temperaments of humankind. One of them is called "The Guardian."
Guardians are observant and cooperative. Protectors, Inspectors , Supervisors , and Providers are the role variants contained within this category. Guardians seek membership or belonging and are concerned with responsibility and duty. Their greatest strength is logistical intelligence. They excel at organizing, facilitating, checking, and supporting.
There are plenty of good things to say about Guardians. But what they have in common is a placing of "the good of the group" above all else. They therefore gravitate toward involvement in things that they believe will support the group (family, community, etc.) You'll see them heavily involved in school PTAs, housing associations, and--yes--churches. Indeed they are typically busy in the service of others, but also have a preoccupation with reminding others of how things are "supposed to be." Anyone can be involved in a fundamentalist religion, but you'd better believe that (for centuries) it's the Guardians who've been creating the legalistic, authoritarian structure within which they operate.
These people think it's their job to dutifully remind you of your obligation to do what's right. Further, "what's right" is what they have become convinced is right. Anything else is either a misunderstanding or a demonic influence that profoundly affects their very bowels. Trying to explain to them that their way isn't the only way seems to upset their sensibilities, since they are not happy unless everyone is performing their rightful tasks, respecting authority, working together toward the same purpose.