I'm not quite sure why this a) is restricted to 15 people or b) requires sponsorship as from the information there it seems to be essentially a book-club type f

I'm not quite sure why this a) is restricted to 15 people or b) requires sponsorship as from the information there it seems to be essentially a book-club type format. Perhaps I'm missing something - are there not already groups/clubs that get together and do things like this?