Because doing a dive kick right above the ground is incredibly strong. You can mix up between empty jump throw, empty jump low, and vary the block stun and timing of your jump attack to make defending against all the options really difficult. You can fake an empty jump and catch people flinching with a super delayed dive kick, for instance. Height restrictions play an important role both on the way up and the way down.
Don’t really know how to respond to this. If you want to equate “random” with “sometimes it works, other times it doesn’t” without considering the source, then… I suppose? But if you consider the fact that each player can improve their skill and eliminate the random factor entirely, then you have to search for a different word than random, because that implies a lot of things that aren’t true about DPs.