Before MADD pushed drunken driving laws, fraternal organizations were very common. Elks, Eagles, Oddfellows, and a bunch of others used to have places men could go to gather for drinks and conversation. Most of them did and do fund charities to keep a non-profit status. The Flintstones were a reflection of the time they were made, so Barney and Fred belonging to a "lodge" was normal and expected.