was
secret, can be among them. Another prominent reason is simply a permanent intent to switch accounts--mastina is my main, not mastin2 and certainly not Mastin, even though those accounts were mine and predate the creation of mastina. However, even discarding those, alts often can have gimmicks attached to them, which means that roleplaying is part of the fun behind them. There's no pragmatic function (except when there is--see below point), but an alt can be a wonderful opportunity to just have fun immersing yourself in the character established.Pragmatically, alts are often largely used to explore. They are an escape. This does not need to require secrecy--secret alts obvious have greater freedom to explore, but even a public alt can end up able to play in a different way otherwise unavailable to them on their main. This experimentation is rather excellent for growth, since the curiosity behind "what if this were different", "what if this wasn't there", "what if this WAS there", and so on and so forth, traits easily investigated on an alt but which can be harder to do on a main which is 'established' as it were, allows for improvement and evolution in playstyles.
tl;dr, alts not only give extra fun for the game, but also give an opportunity to explore and potentially grow as a player by forcing someone to think outside their established mold.