Because Russia hasn't decided to side fully enough with us on Iran or Syria I suspect.
Just a guess on my part, and that isn't worth much.
I'm sure that is part of the logic, but it's kind of a self-fulfilling prophecy. If we poke them in the eye, they are going to poke us in the eye.
Or, to put it more succinctly, our current policy of poking them in the eye doesn't seem to be working.