Answer
The main reason vertical polarization is so widely used is that these antennas have a low angle of radiation enabling a large portion of their radiated power to be radiated at an angle close to the earth's surface (i.e. Horizon).
The main reason vertical polarization is so widely used is that these antennas have a low angle of radiation enabling a large portion of their radiated power to be radiated at an angle close to the earth's surface (i.e. Horizon).