I had not known of such "clubs" but there was a sort of fad around taking "personal vows" back in the 70s -
For example, vowing to pioneer after working full time a certain number of years, couples vowing to not have children, and the like.
As I recall it, even in the literature and within the CO's visiting remarks, there was a lot of strict talk about how important it was to take these self-imposed vows very seriously and not break them. Pioneering itself was sort of vow, like being John the Baptist, they said.
I thought at the time - what kind idiot would take a voluntary vow in this repressive culture in the first place? As if we didn't already have enough unconfortable or unlivable rules...and - if you did, why tell somebody. But, obviously, some may have thought this made them look holy, sort of like a Nazarite...