No we don't necessarily, and ideally Morata, Dybala & Berardi can do that in the future.
But young talents often take time to settle in and underperform or flop at times, Morata has done very well this season but still needs to prove that he can hold up to his new found fame. Of course someone like Cavani would be ideal, but we don't have the money for him, so a player who's relatively cheap and pretty much certain to perform is great.