dorsiflexion is extremely important in athletic development, not because it’s your first layer of protection, but because it allows you to actually drive through the glutes and quads straight down into the ground to produce vertical force 

the main force you’re overcoming in jumps and sprints is gravity 

so the more dorsiflexion you are capable of, and the stronger you are in it, will increase your ability to overcome gravity and produce vertical force. Which is the main difference between faster & slower animals, people, etc