Ekko Damage Scalings

From what I've seen and heard people were curious as to why Ekko is full AP with his damage scalings with out any type of AD scalings. I've Played Ekko on PBE servers and I see how the AP scalings make sense but I'm curious as to why he doesn't have any AD scalings so at all. I create this discussion because from what it looked like in the trailer Ekko was using more so attacks than his abilities other than reversing time(his R). I'm asking if the people in charge of champion scalings to add at least a little bit of AD to his abilities. I've built Ekko with AD with the current kit but I had no poke power which made my build a late game build but I had too much pressure in lane and nothing to stand up to my opponent with Build Essentials: