This is very useful for vhf and uhf radio communications as well, which are normally* line of sight.
In fact, the adsb-receiver[1] software package for setting up an aircraft tracking station includes a neat feature where you can use HeyWhatsThat to calculate maximum line of sight distances to aircraft at various altitudes and include these contours on your aircraft tracking map.
* atmospheric phenomena such as density or humidity differences or reflections from other aircraft, the moon, or even meteors can enable reception over the horizon.