I would guess this had less to do with religion and more to do with safety. Depending on how many people were involved, a private home is rarely outfitted in a safe manner for large numbers of people. Doors may not open outwards, exits may be limited, layout of the house may make fast exits virtually impossible in case of fire and I could go on.
As for large parties, bible studies, confirmations, etc., check your zoning laws and I'd guess there is something in there that gives the local officials the authority to close down a bible study, confirmation or party if they feel the amount of people exceeds the safe limits of the size of the home.
Melody