I'm developing a mobile social game, it's a puzzle with a social layer similar to the one in Candy Crush Saga (limited lives, can send life requests to friends, facebook leaderboards, etc). I know all top mobile social games have a backend, but I don't understand what's the purpose of it, is it only to persist game data? Assuming I'm not interested in persist game data online, do I need a backend server?
My idea was to handle all players' interactions through facebook (life request, leaderboards, etc). Is this possible without my own backend?
Any information on what are the benefits of having a backend for a mobile game is welcome.