You don’t need to, but it really helps. Soaking your rice (and lentils) at least an hour before you plan to use them is always a good idea. It doesn’t just help cut down the cooking time, but also reduces the levels of arsenic in it.  That’s not all- soaking the rice also makes it easier to digest- the process helps cut down the levels of phytic acid, which in turn, also makes the nutrients in rice easily available.