You need relatively hot water to make steam but there is plenty of heat left over in the discharge water. That is why they need all that cooling water and those big stacks.
I believe the sizing of the cooling towers is based on dissipating all of the heat from the reactors without being able to convert 1/3 of it to electricity, as it is typically done during normal operation.
Most commercial power plants have steam use/reuse systems to increase plant efficiency. Typical items include preheating feed water, using steam driven pumps, steam driven vacuum pumps, etc.
Unfortunately, most applications require high pressure steam. The available "waste" steam is generally low pressure and high volume. Those characteristics makes it difficult to transport the energy any great distance where it can effectively utilized.
