Such a ban is pointless unless you block every business which does business with Russia and that is not possible. Eastern European countries, ex soviet satellites, etc would have to pick sides and that kind of final decision isn't in our best interests or theirs.

If you only block doing business with Russia, then middlemen in other countries will just have to be go-betweens making a politically inflammatory action (blocking a world power) that wasn't actually effective beyond being offensive.

Blocking Crimea is a symbolic but also mostly ineffective practice done to make a statement. Making that statement about the entire country wouldn't be prudent.