Another key point: the type of people who are politicians in America (especially local politicians) are "joiners," and tend to join many different community organizations for 1) the social connections and 2) the chance to be known just enough by just enough people in their town/district for electoral reasons. The type of person who is civically engaged is the type of people who recognizes the intrinsic value of places of worships as community spaces, even if they don't personally have devout beliefs (or beliefs, period).
Yep. The Rotarian personality, basically.
Religious leftists would also do well to keep all this in mind when deciding how we feel about certain stereotypes of irreligious people--something that took me a while to learn myself.