First of all, you need to understand that the water you are talking about is essentially different. The steam which powers the turbine is cooled by the condensate. What goes to the cooling tower is recycled water. These are two different things for power plants.
The main reason is that our units are usually the condensing type, which uses a condenser to condense the exhaust steam and then condenses it to create a vacuum. This allows steam to flow smoothly through the turbine and collect the working fluid. This part of the water has very high requirements, it is very clean and has high requirements for conductivity and ion content. It must be specially made.
Circulating water is used to condense the exhaust steam. The cooling tower you mentioned is used to cool circulating water and is used in areas where water is scarce. PFor example, there are many places where there is no shortage of water and which directly use water from rivers and lakes.
You should understand now.