One of the most powerful methods of transmission is microwaves. These transmissions operate in a similar manner to radio technology. With the ability to transmit over long distances, with no physical wiring, installing microwave systems can be more cost-effective. Mountainous regions are prime locations for these towers, and require less maintenance than other solutions.
But microwaves do require “line of sight” communication. This means that transmissions are only successful when microwave towers are free of obstruction. So, mounting them the higher the better prevents the curvature of the Earth from impacting this line of sight.