Why most of the unhealthy champions are AD ?

coincidence ? i maybe a noob player but i don't have any problems playing vs Ap champs ? the only problem was kata and lb but they got their kit fixed with the assassin update and i can easily fight them , nothing more than that. also ap champs were unhealthy for only a short duration like morde
is an exception but he is getting a nerf soon .. EDIT : i don't see why should this topic deserve downvotes am just talking about truth , or is it because i am silver everything i say is not right even if it was ?