Why does electrical power transmit high voltage?

In the way the voltage is higher the current decreases in same proportion and then losses are reduced in transmission lines that means you need conductors with minor gage.

because of losses (voltage drop) along the transmission line

to reduce the voltage drop

The power or energy flowing through the wire is the current multiplied by the voltage

power = current x voltage

This means that you can transmit the same amount of power with a low voltage and a high current or a high voltage and a low current.

The wires resist the flow of current, a bit like friction resisting your motion as you slide across a floor. It takes effort (voltage) to push a current through a wire, the smaller the wire the more effort it takes.

This converts electrical energy to heat so there is less energy left to do something useful at the other end. The larger the current the more energy is lost.

The higher the voltage the less energy you waste, so power is moved long distances at very high voltages as high as 400000V, but this produces other problems. If the voltage is very high an electric current can flow through the air creating sparks, and can easily flow through your body electrocuting you, so everything has to be designed carefully and made very large.

So, different voltages are used in different places depending on the amount of power that has to be transferred and how easy it is to make the high voltages safe. So, power is transmitted around the country at 400000V, around a region at 132000V, around a town on wooden poles or underground at 11000V, and to your house at 240V

To reduce line losses. As line loss is directly proportional to the current flowing through it. By stepping up voltage, the current is stepped down by the transformer. Keeping Power constant i.e Law of Conservation of Energy. Electrical Power is product of current and voltage. If one goes up the other goes down.

To reduce power losses during transmission as some energy is lost in form of heat when current flows. So to transmit same amount of power low current and high voltage is used.

Because in long Transmission lines power is lost at the receiving end due to resistance of wire and heating of wire.Therefore Electrical energy is transmitted in high voltage.

In order to prevent many factors  due to line losses and other controlling factors of overhead cables for long length