Originally posted by: XanBcoo
Sharingan can't copy Rasengan as it is completely chakra control - I'm even pretty certain it states this in the anime (not sure). And I suppose he just never wanted to copy Kage Bunshin.

In any case, you've seen them both copy justu, they just prefer not to focus on that aspect of the sharingan like Kakashi does.
at the beginning, Kakashi's justu was only Chidori....well im sure of it thats why thay call him Copy Kakashi