smoke canisters, AFAIK, never worked well enough in WW2 for them to incorporate into standard design. Think about it: it just doesn't make sense. You can hear the tank from a mile away. smoke is good concealment for infantry, not a 60 ton piece of metal that whirrs and clanks its way through streets.
Gaming wise, they'd have to make the smoke so thick that it looks like a sandstorm, AND somehow disable the red outline that you get when you mouse over something in a smoke cloud. Neither are great ideas.