Maybe they removed for better game-play reasons? If your troops fire and there is large smoke that lasts for awhile and you cannot even see your troops. It effects game-play as you cannot see them re-load, take hits, die or anything else for that matter.
Personally I like it the way it is, un-modified.
When you're a file closer or officer and you're behind the firing line, after the initial two volleys and the battalion commanders orders fire-at-will (Civil War-era practice--we're not cool enough to do platoon firing) you already can't see the enemy through the smoke. Which is why, historically, the color company--and its neighboring companies--always took double or triple the casualties: because all you can see of the enemy is their flags.