why does the jungler never go farm under pushed turrets when asked for help?

Hello i actually never flame my junglers but im just curious maybe im missing something, but lets say im an assasin so i pushed the wave to turret and go gank bot, got a doble kill (great start) but the mid laner realized that i went to gank, so he decided to shove and try get plates. Im low so i have to recall and ill dont make it in time but i see on the map that my jungler is right around the corner, so i ping it to help mid (even ask in chat to pls farm under turret) i see it as a win win because the jungler can farm more gold, the oponent dosnt get plating and i get some pri o when im back, but 9 out of 10 time the jungler just completly ignores me and the oponent get 2 plates.

am i missing something or is my jungler just not very good?, (also at that time the jungler is just farming camps not ganking other lanes)