In skill_proto there's an intentional 3 seconds difference between duration and cooldown. Is there a reason for that?

[covfefe 35]

Basically the title. While going through skill_proto today I've noticed a pattern of a 3-second delay between the duration and cooldown of skills. In the game that's kinda annoying.. which made me wonder, is there a legit reason for that, that I may not be aware of? Why not have the same seconds in duration and cooldown which would be more convenient for the player..?