Why don't current hydroelectric plants use the siphon principle to produce electricity?

There is hydropower generation using the siphon method, but its power generation capacity is very low, because hydropower generation depends on water pressure and flow. Where a dam can be built to increase the water height, most hydroelectric power plants are seen. use today The ability of water heads to produce electricity, such as the Three Gorges hydroelectric power station. If the amount of water is large and the water height cannot be increased, tubular power generation is used, using the large water flow to drive the generator to produce electricity, such as Danjiangkou Power Station. For a small drop, regardless of the method used, the energy of the water is not large, because the energy will not be amplified by a conduction method