[Haskell-cafe] why is Random in System?

I've noticed there's a convention to put modules having to deal with randomness into System.Random. I thought System was for OS interaction? Granted getting a random seed usually means going to the OS, but isn't the rest of it, like generating random sequences, distributions, selecting based on probability, shuffling, etc. all non-OS related algorithms? I'm not sure where I would expect Random to go, perhaps Math or maybe the toplevel, but under System seems, well, random... I notice random-fu puts it under Data, which is also not where I'd look, except that you always look in Data because everything goes into Data... but algorithms dealing with random numbers aren't really data structures either, are they?