Monads useful?

A LOT of monad tutorial on the net. Just one example; the State Monad

DrawScene to State Screen DrawScene ; still pure.

main = drawImage (width,height)

drawImage :: Screen -> DrawScene
drawImage screen =
    drawPoint p screen
    drawCircle c screen
    drawRectangle r screen

drawPoint point screen = ...
drawCircle circle screen = ...
drawRectangle rectangle screen = ...

main = do
    put (Screen 1024 768)
    drawImage

drawImage :: State Screen DrawScene
drawImage = do
    drawPoint p
    drawCircle c
    drawRectangle r

drawPoint :: Point -> State Screen DrawScene
drawPoint p = do
    Screen width height <- get
    ...